power amp will give it the punch you want but have no reqs for types u can try. I have a Sony avreciever hooked up an old set of cerwin vegas. the sound was very dull hooked up an old fisher intigrated Amp an bam! lots of base ,thump and I could feel the music again. Just make sure amp does not over power speekers. good luck
i am no audio expert so take what i say with consideration. i think rotel and adcom or maybe marantz have amps that would be more than enough for the 603s and match them well. the 3480 already has like 120 wpc so its hard to imagine how loud u play your speakers. u should be safe with the power ratings for the above mentioned companys' products since they give honest ratings and usually with lots of headroom. happy hunting.