I sat in 310, row 11. The tickets were only $20 a piece so I figured why not? My girlfriend who doesn't know much about hockey tagged along.
The pepsi center is a nice venue but don't get any seats in the upper level corners, you'll get you knees smashed against the seats. If you sit up high, plan on rubbing elbows. We're talking smaller than airline seats in coach. Not the most comfortable seats.

You will definitely want lower level seats for the Avalanche to get that up close feeling to experience all of the rough housing that hockey brings. But you're going to have to open up your wallet for those seats. And concession prices; forget about it...