Asking for guidance on my first hi-fi system...

Hello, this is my first post here and I am hoping to gain a little confidence in making a purchase of an integrated amp for a nice two channel music only system. I recently built my own speakers, (the Jim Holtz Mini Statements) and auditioned them at my friends house on two different high end audio systems.... Rogue, Electrocompaniet, Van Alstine are a few names I remember of his gear. He helped me confirm that my speakers sound very nice and are a good starting point to build upon. My budget is 500.00 or less for an amp. Currently I use an Onkyo HT-R520 home theatre receiver, set on "Direct" listening mode. Obviously, my speakers don't sound as good with the Onkyo. I believe the bass is over emphasized and the mids and highs are a little lacking in detail.
Here are my objectives:
1. Stay within budget
2. Find something that will sound better and resolve the weaknesses of the Onkyo

Currently I am interested in a 300 to 400 dollar Carver CM 1090 integrated amp. Would this be a wise choice given it's age? or should I be looking at a new NAD, or ?????

Any and all help would be greatly appreciated!