please help with new 5.1/7.1 build

What is your budget for total system cost? After we know that we can help you out. But remember most of this stuff is subjective, so listen to the advise but go out and demo different speakers and systems so you can hear for yourself what you like.

just a note... the only "real" difference between the Polk Monitor line and the TSi line is upgraded esthetics. For all practical purposes the "guts" are the same, or very nearly so, and it comes down to a huge price differential for improved "looks".

To compare apples to apples, you would need to consider the TSi500 as a direct competitor for the Monitor 70's. The TSi400 = Monitor 60.

With www.newegg.com pricing and free shipping, the Monitor series wins hands down. (if you can wait and watch for one of their coupon sales on the Monitor 70's, you can save even more $$$).

As to a receiver, start with these models in each manufacturer's lineup and then move up-price until you find the receiver with all the "features" you want. Denon 590, Onkyo SR507, Yamaha V465, Pioneer 819. I have not keep up with the Harman/Kardon lineup, but I'm sure others will help out here. Each of these models has full audio and video processing, including decoding lossless HD audio codecs, over HDMI cables.

If you want to consider another speaker line-up, price out a full system of Infinity Primus speakers, starting with the P362 towers. Unless you find a great sale, they are a little more expensive than the Polk's, but they are the direct competition to the Polk Monitors as a super "bang for the buck" speaker setup.

For music polks were too bright for me. The monitors are the same speakers as the tsi's but in a older cabinet. Speakers don't wear out unless they've been abused so your fronts may still be ok and just need to add rears or buy new fronts and move your Missions to the rear. Newer speakers may sound better when you go audition them because they are generally brighter sounding. This might be ok for HT but not for music.

your welcome ! I would also consider the Denon a/v receivers - excellent built and solid specifications. They can be a little fussy to set up, but a great member of this forum, "batpig", has written an excellent "Denon dictionary" to translate Denon-speak to instructions mere mortals can understand. http://batpigworld.com/

Frankly, ANY of the major brand a/v receivers will do well. They will all drive the Polks or Infinities to normal levels and above. Your room size will have an effect on how much power and "overhead" you will need out of a receiver.