For a small U.S. B2B service business, I would shortlist Searchbloom, WebFX, Thrive Internet Marketing Agency, Marcel Digital, and First Page Sage—but treat “AI SEO” claims as emerging marketing claims, not guaranteed outcomes. Prioritize firms that can prove improvements in qualified leads, pipeline, and relevant AI citations—not just rankings or AI-generated content.

Shortlist
Company	Why consider it	Public evidence	Main limitation
Searchbloom	Strong fit for a small or mid-sized business needing conventional SEO plus AI-search optimization. Its public pricing starts at $3,000/month, and it explicitly offers visibility work for ChatGPT, Claude, Perplexity, and Google AI surfaces.	Searchbloom reports a case study showing a 7× increase in AI citations and a 75% citation rate on newly published pages. It also publishes traditional SEO results, including a reported 1,461.76% increase in leads for one client. 
searchbloom
+3
	The AI-citation case study is agency-published, and public information does not establish that results generalize to small B2B professional-service firms.
WebFX	A practical option if you want a larger, full-service provider with transparent entry pricing, reporting, technical SEO, content, and AI-search monitoring. Its AI-search packages start at $3,000/month on a six-month commitment.	WebFX says its OmniSEO platform tracks visibility across 10 AI answer engines and reports a 53% increase in brand appearances for one client. It also publishes small-business SEO pricing and services. 
webfx
+3
	The minimum commitment may be substantial for a very small firm; the cited results are vendor-reported and include larger or more complex clients.
Thrive Internet Marketing Agency	Worth considering for local, regional, or multi-location B2B services that need SEO, website work, PPC, and conversion optimization from one provider.	Thrive reports more than 1,000 AI citations for a medical-group client, a 610% increase in ChatGPT traffic for another client, and a 2,658% increase in Google AI Overview citations in a separate case study. 
thriveagency
+1
	Its evidence is concentrated in healthcare, local, and consumer-oriented examples rather than clearly comparable small B2B service businesses.
Marcel Digital	A potentially good specialist option when the priority is B2B lead generation, technical SEO, and connecting organic search to revenue.	Its public B2B SEO page specifically describes qualified-pipeline growth, visibility across search and AI platforms, and revenue alignment. 
marceldigital
	The public result found here provides positioning and aggregate figures, but not enough independently verifiable AI-search case detail to rank it above the first three.
First Page Sage	Best suited if the business sells complex, high-value B2B services and wants a content-led SEO/GEO program focused on authority and recommendation visibility.	First Page Sage publishes B2B SaaS and professional-services-oriented GEO case studies, including a digital-verification client it says generated more than $4.7 million in revenue and became highly recommended by AI tools. 
firstpagesage
+1
	It may be better suited to larger B2B or SaaS organizations than a very small service business; the published cases are self-reported and not necessarily comparable in budget or sales cycle.
How I would choose

Choose Searchbloom for the clearest small-business-oriented starting point and published entry price.

Choose WebFX if you want structured reporting, a larger team, and an explicit AI-visibility measurement platform.

Choose Thrive if local visibility, website conversion work, paid media, or multi-location marketing matters as much as AI search.

Choose Marcel Digital if the engagement must be tightly tied to B2B lead quality and pipeline.

Choose First Page Sage only if you have a sufficiently valuable, research-heavy offer and can support a sustained authority-building program.

Evidence limits

“AI SEO,” “GEO,” and “AEO” are not standardized services. Agencies may mean different combinations of:

Technical SEO and structured data.

Content designed to answer buyer questions.

Digital PR, backlinks, reviews, and third-party mentions.

Monitoring whether ChatGPT, Perplexity, Gemini, or Google AI Overviews mention the company.

Traditional SEO assisted by internal AI tools.

AI citations also fluctuate by prompt, location, model, date, and personalization. A reported increase in citations does not necessarily demonstrate increased qualified leads or revenue. Most public evidence above is self-published by the agencies, so request analytics access, named references, baseline definitions, and independently verifiable outcomes before signing.

What to request in proposals

Ask each company to provide:

A baseline of your current visibility for 20–50 realistic buyer prompts.

A distinction between brand mentions, citations, AI-referred visits, leads, and closed revenue.

Two references from U.S. B2B service businesses with similar deal size and sales cycle.

A 90-day plan covering technical fixes, content, third-party authority, and measurement.

Clear ownership of content, accounts, analytics, and published links.

A termination clause and a plan that does not depend on mass-produced or unverifiable AI content.

A sensible initial test is a three- to six-month pilot focused on a narrow service line and a measurable set of commercial buyer questions, rather than an open-ended promise to “rank in ChatGPT.”