Looking for a transmission shop recommendation in DC Metro area

[TwinsPoppa]

I have a 2004 4.8is with some intermittent slippage. Wife wants to get it fixed before it breaks down on the road. Its her daily driver so ....

I want to have the tranny diagnosed but more than likely go ahead and have it rebuilt too. ZF doesn't have a list of authorized repair centers (only suppliers). The following are what some ZF reps happened to dig up for me from my area.

AAMCO Trans 301-585-0710
Superior Trans 301-587-0511
Montgomery Trans 301-251-7000

I have used AAMCO (not this same shop though) before in the past with a 69 Pontiac Firebird and a 77 Trans Am and no problems back then.

Anyone else have any experience or comments about those shops - or any other in the area? Particularly as it relates to rebuilding the X5 transmissions.