best integrated amp for under 5K

PS Audio GCC series. You can get either a GCC 250 or GCC 500 for about $2500-$3500. Read the reviews. They are awesome, differentially balanced full function remote

I always liked PS Audio. Another one to consider is the Musical Fidelity A5.5: 250 wpc and about $3K.

They also make the KW 500 at 510 wpc and a tube preamp section. MSRP is $7K, but most of the owners who reviewed it at Audioreview.com got theirs for between $4100 and $5500.

I've heard the high-powered MF integrateds, and there's hardly a 2-channel situation the higher powered ones couldn't handle. They're very fast and clear.