The advice given by other posters about using your budget to upgrade other parts of your system at the same time you buy an amp is sound, especially given your speakers. I checked out your Ushers. Fine speakers, but output limited with two midbass drivers and no dedicated woofers. If rock is what you mostly listen to, you need a high output speaker.
Ideally, you should consider horns or powered speakers like ATC or Genelec. Assuming you are not ready for that, however, I would look at a pair of used Vienna Acoustic Mahlers (+/- $4,500 for a mint used pair). They are 90 db. efficient and each speaker uses the same two 7" midbass drivers as the Wilson Maxx II, plus two 10" woofer, all with ported bass loading -- they go LOUD. With the $3,000 left over, I would buy the highest powered FPB series Krell you can afford or a Levinson 334 or 335 (ideally, a 336).
As for my previous post, wattage in amps is often misunderstood and leads people to buy amps that cannot do what they are purported to do. In solid-state (transistor) amps, power supply capacity is most important, which is why a very high-end 150 watt/channel amp can drive a speaker better than a typical 300 watt/channel amp. Krell will give you current, as will those Levinsons (your Proceed weighed about 1/2 of what a 334 weighs, incidentally) . I look more closely at the weight and price of an amp than the wattage rating - power supplies add weight and cost.
I would use the money left over from swapping out your Ushers to buy a Doge 6 CD player. It has a high capacitance 6-tube triode output stage with tons of punch and no lack of finesse (sells for $5k in Europe due to the import duty, but only $1,400 here).
