Welcome to Atlanta! My work is near United Gwinnett and that's where I bought my car so I go there for service. The customer service has been good but they aren't really fans of mods. I guess most here like United Roswell best since Dan the parts guy is now there also.
Solo seems to me to be a great choice for trickier services such as an LSD or even coilovers. An FMIC is practically a do it your self mod so anywhere should be fine. I have my basic stuff done at my friends shop that specializes in Range Rovers (The Shop in Norcross, 678-352-4900). They did my FMIC btw.
The only car washes on my BMW that I didn't do myself were at the dealer. My car is BSM so I'm very picky about swirl marks. The dealer did an OK job avoiding swirls but honestly I should have just told them to not wash it there.
BSM, Blk leather, 30%tint, Injen, RR OCC, MadDad Whisper, donut spare, 19x8.5et43fr 19x9.5et45r Volk LE37's, rear fenders rolled/pulled, Nitto 555 225/35fr PSS 255/30r, KW V1's, AR coated catless dps, Cross strutbar, CF grills and license plate holder, rearseat removal, iCarbon diffuser and front lip, ETS black anodized FMIC, M3 control arms, Quaife, ER chargepipe, ForgeDV's, Topspeed Custom Tune, V3sims, Braille