Help with stepping up from AVR to Amp/Pre-Amp

I have a Marantz 6005 AVR, Arcam CD72 and Oppo BDP 93 for DVD's. Just upgraded my speakers to B&W 683's and sense that the Marantz won't cut it. If I need 5.1 for movies and want to step up to the amp/pre-amp world, any suggestions? I want to make the most of my speakers but be somewhat budget sensitive (maybe $2000 total or less).

Thanks- Scott