I use the one on Soi 6, there is a restaurant towards second road end named the Victorian or similar (it's the only respectable look establishment on that road).
I think their called "first class visa" The have been reliable, knowlegible and their prices are about the same as everybody else's prices.
I have obtain visas, while in Thailand, then left and come back to activate them. The Thai Government is not looking that closes. I recommend you not worry so much.
I was shopping around for visa options, marriage or retirement. Visa agents quoted me 10-15K to do the retirement visa. They quoted me 60K to do the marriage visa.
Last time I flew into Thailand (couple of weeks ago), they pulled me aside and yelled at me about using a tourist visa, for 10 years. They let me in, it wasn't a big deal, but they are starting to pretend to be more serious.