What size room and how far are you sitting from them? What sub do you have Velodyne ranges from $300 to $6000 some have high pass outs and will handle your crossing?
You probably don't have to spend $500,
I like the Topping TP60 it sounds great, I have had one for a while and have used it a lot and it has stood up great to loud playback for long periods of time... Very clean sounding amp..
The apa150 also works well, its class ab, and a work horse for sure..
But with them you will have to do something for bass management, I like FMods, and I know a few "others don't" but they do the job and don't add or take away anything (except what they are supposed to)...
these have sub outs
ONKYO A-9050 Integrated Stereo Amplifier | Accessories4less
YAMAHA A-S300 Integrated Stereo Amplifier | Accessories4less
YAMAHA A-S500 Integrated Stereo Amplifier | Accessories4less
Another option and sometimes a very good one is a real receiver {not an avr "others" also think avrs sound as good as something more direct by pushing the "direct" button, but IMO it doesn't...
YAMAHA R-S700 Natural Sound Stereo Receiver | Accessories4less
Marantz SR4023 80w X 2ch Ci Friendly Stereo Receiver | Accessories4less
DENON DRA-697CI AM/FM Multi-Source/Zone Stereo AV Receiver | Accessories4less
If you need bass management, I think I would go with the A-s500 {if you can stretch the budget the A-700 is nice I own one and it sounds good}, if you don't mind using an fmod or an external digital cross over to cross the bass form your books, then I would go with the topping tp60... its a toss up... if you do stretch the budget to the a s700 you are in the same neighborhood as getting a USP1 and a UPA200 amplifier? hard decisions..
The firs thing to consider is bass management