Marantz SR700 cost to repair too high... advice?

I purchased my home theater system about 12 years ago. I have a Marantz SR7000, Monitor Audio Silver 5i LR, Monitor Audio Silver 10i C, Cambridge Soundworks surrounds (I forget the model but they are dipole) and sub.

Recently I've been getting crackling and then a large "whoomph" before losing sound in my center channel. I took it to a reputable stereo repair shop and they said that the center channel is fried (my term not theirs) and that the parts and labor to replace the appropriate components would be about $350. They actually recommended that it wasn't worth the repair work since I could get an updated receiver of similar quality for not much more in price.

It's been a long time since I've researched this stuff and would appreciate some advice. What are some mid-fi receivers that I should be looking at? Are Marantz, Dennon, and Onkyo still the brands to be concentrating on ?

I think I paid about $800 for my Marantz but don't really want to spend that now. Maybe I could get the same quality as a 12 year old SR7000 for cheaper now? I'd like to keep it around $500...

I use this almost exclusively for HT but the audio performance is what is most important to me. I know I'd benefit from networking, more inputs, etc, but I want to emphasize that sound performance, not features, is what I'm looking for.

Should I spend $500 for something new or $350 to fix what I already like but which is very out of date?

Thanks for your help!