I'd say it would be possible to make noticable gains in sub and receiver w/ $700 IF you did a DIY sub. Something like a TC Sounds 12db-500 ($135) and PE Bash 300w plate amp ($105) in a 4 ft^3 box tuned to 22hz would be a pretty noticable step up and equal or come REALLY close to a SVS PB12-NSD.
For the receiver something like the Onkyo SR604 ($330, Accessories4Less)or (if you could stretch your budget just a tad) the SR674 ($550, Accessories4Less) would give you HDMI switching and LPCM audio for use w/ your HD-A1 and Tivo Series 3. If you want to stick w/ Yamaha you could get the HTR-5990 (mass-market version of the RX-V1600) for $550 from
www.electrified.com . The HTR-6090 (mass-market version of the RX-V1700) can be had for $640 from
www.zoommania.com but that would pretty much kill any budget headroom for a DIY sub. You can also order the HTR series online w/ less worry than the RX series as the HTR warranty will still be honored.
