Is there a "decent" receiver out there that could interface with the McIntosh MXA70?

Thanks Erik!  Your suggestions are quite helpful.  Yeah, I'm still addicted to stereo.

I use a similar setup with an Anthem MRX 540 and Luxman 509ux. 

Here's what I think you should do though.  Use a digital optical cable from your TV to your MXA70 to get perfect stereo TV sound.

If you still want to add surround sound, the MRX 540 or 740 are ideal enhancments.  More information on page 26 and 27 of the MXA user's manual under "System Thru Operation."

Is there a decent (meaning less than $400) receiver out there...

No, not really. Not sure there are any decent receivers regardless of price, might be a couple.