ROTEL VS YAMAHA RXV1500

With your size room and sensitivity of your speakers, I think that you'd benefit more from getting an amp with a lot more power. I think your Adcom is 125watts? Try something out with at least 300watts, 400watts would be much better. The Yamaha will be fine as a pre.

I'm sure that others will chime in but I think that Yamaha will do an excellent job with processing. I think you'll hear a nice difference by changing out that Adcom amp. A couple of reasons, better quality amplification (I'm not really an Adcom fan) and combining that with the proper amount of power (with reserve headroom), will yield an improvement.

I've been very happy with my Sunfire amp and for the cost, I think it offers a tremendous value (used). I've heard/read really good things about B&K. These are two that come to mind that will not break the bank and offer 7 channel amps. I would personally try and find or wait for one of the older model Sunfire Signature's to come up. They were originally 400watts/ch and then version 2 was 425watts/ch.