I have almost the same amp setup as you, a GTP-502 and the GFA-5400. I have them paired to some NHT ST4s though, and dont see a need for a sub. I think te Adcom amps are not too bad at all. They are not the sweetest sounding amps out there, but are good affordable power, and sound decent. My brother thinks that they are a good match for my speakers, him seeing my speakers as warm, and the amps as clinical and a touch recessed and cold, hence matching well. I dont know if I fully agree, but I do like the sound that I get.
The main thing is that you enjoy your setup and hav fun listening!
D

