Have $600 Need input on upgrade for Acurus Amp

I am looking to upgrade my Acurus A-80 amp and would appreciate some input.

Need something to deliver more power to my new 4ohm RS-722s from Parts Express (speaker kit that uses Dayton Reference Series).

I am a big fan of high value / bang for your buck audio and would like to spend no more than $600 (new or used). The A-80 has served me VERY WELL so I am considering a more powerful Acurus amp but would like to explore some options? What about Parasound or NAD or.....? Any thoughts on the Pro Audio offerings? The Behringer Amp looks interesting but seems to have some quality control issues?

My pre-amp is an Acurus RL-11.

Thanks in advance,
How about Aragon? I went from an a200 to a 2004mkii and the difference in smoothness was incredible. Much more refined.
Check out a used Rotel RB-1070(130 wpc) or RB-1080(200wpc) in the $400-675 range. While Rotel's preamps tend to be on the hard/sterile side of neutral, I found their amps to be very, very, good for the money. I owned the 980BX about 6-7 years ago and it was great with slightly warm speakers.

Also look into used Marsh A200 amp(200wpc).
Wyred4Sound stero amp. Call them for availability
If you can go a bit higher try the ube Audio Design 125 monos. If not then a McCormack DNA-0.5 used or DNA-1.
I agree with Darkmoebius. Rotel and Marsh are both very solid options. So is the Aragon.
I use an Accurus 200 or 250 for the surround channels. PS Audio HCA-2 digital amps via XLRs are in a totally different league. They go for 650-700
McCormack DNA .5 or 1.