Van_G, welcome
it looks like you've chosen well as far as new speakers are concerned. I think you will be very happy with the Axioms, and the upgrade to a VP150 is probably the right choice if funds allow (especially if you have a large HT room).
I'm not completely familiar with your NAD setup. I'm sure it's just a newer version of the
NAD 160/270. If that is the case, you've got a very nice 2 channel setup. But if you're looking to wade into the HT arena, you'll need a new processor. AV receivers like the
Yamaha RX-V1400 are a very popular choice around here because of their auto calibration features. They also have preout connections so you will be able to still use your power amp to power your main speakers if you wish. This shouldn't be a necessity though, as the Yamaha will have plenty of power to drive your mains to eardrum-shattering volumes.
I don't think you have to worry too much about the DVD player. As you can see,
here the reviews on this model of DVD player were quite good. Panasonic has a reputation for building quality DVD players at prices a fraction of most other company's players. So realistically, I don't think you'd see a drastic improvement in quality sound or picture to upgrade your DVD player. However, if you think you want to get in to multi-channel music playing like SACD or DVD-Audio, here's a coule of popular choices:
Denon 2200
Pioneer DV-563A
these are two highly regarded players that won't break the bank. Good luck!
