ok...you don't mention specifically where you are, but your best bet is to find an Enrolled Agent near you. Enrolled Agents can represent you in front of the IRS and speak on your behalf. Please see link below to find an Enrolled Agent near you:
On the left side of the page is a link to find an Enrolled Agent by zip code/area.
You are free of course, to work with the agencies you already named, but please keep in mind that they are basically just brokering a "Offer in Compromise" with you & the IRS. and most charge quite a bit for this service. Please be sure to check any company you are considering using with your local
Many professional tax preparation practices have EA's working for them. (H&R Block has jumped on that bandwagon, and there are many more that have followed suit) You might find that these places will broker an "Offer in Compromise" at a much lower rate than those companies whose sole source of income is from this type of service.
Again, a quick check with your local BBB should help "weed out" some of the contenders.
I wish you the best of luck.