The up-grades in a newer receiver over your vsx-29 would be too numerous to list. Just head over to a manufactures website and look at the specs page of any receiver in your price range. HDMI, 24/192, room correction, video processing (if you need it - I suspect most really don't), advanced bass management, more accurate speaker setup and adjustments, internet radio, streaming, firmware updates, etc. and ease of use once you figure it all out.
Vintage gear can still be very usefull and enjoyable. I wish I still had my H/K 520, and Pioneer 59txi, and Outlaw 990, and... though I'm not sure what I'd do with them .