What is a good amp that cost no more then 3500.00

Just saw a pair of Aleph 2 monos (100/200 8/4) for only $2800! Can't beat that for a great amp value.
Good luck.

I have tried numerous amps in the price range you are looking in. With the Proacs, the Marsh A400 or the Bel Canto EVO's would be terrific. My experience is that the Marsh is the most neutral and transparent amp around. It may be the best amp, period. The EVO is incredibly clean and fast but not quite as musical as the Marsh....still a great choice. If you are in a medium to small sized room, the Proacs may be friendly enough for a higher powered single ended tube amp such as Antique Sound Lab AQ1006-845. At 22wpc these things have good power into a easy load and are a open window into the performance.

Find a closeout sale on the Aragon Palladium II monoblocks (line is getting new faceplate next year). Bought mine for $3300. Arguably one of the best amps for under 10K. On the flip side, I also second the nomination of the Bryston 4B-ST. You say you want to keep the amp for 15 years, well the Bryston warranty is good for 20.

belles 350a.

if it were by a major label manufacturer, it'd be 2x that amount.

ego audio need not apply.
rhyno

Lots of excellent advice, above. However, Subaru's suggestion for the Aleph2 & Rhyno's for belles are difficult to beat IMO.

I concur that you'll be looking for another pre -- the amps proposed are in far removed league to the Yama (a fine product, nonetheless).