Decent reciever on a budget?

Just getting started on the high end theatre deal.. any recomendations for a good new/used unit on a budget? I've been looking at used stuff from arcam, marantz, integra and rotel. This will also serve as my primary listening reciever for now but I will probably end up using it as a preamp at some point and external amping everything. I'm not so concerned with 7.1, 6.1, etc.. but definately has to be surround and perhaps have phono inputs (although I could run a external phono preamp instead). I know I need Dolby Digital and DTS but what about THX, etc? Any suggestions are much appreciated. Thanks for helping a beginner!