The other side of the coin:
Most rooms simply aren't configured to take advantage of 5 - 8 speakers. Trying to figure out where to put them all for optimum configuration will be a challenge to all but the biggest room. Even then, only a seat or two will be in the true surround zone.
Very few non-movie recordings (SACD, DVD-a) are multi-channel. A small percentage of those are actually recorded well enough to justify all those channels.
It is impossible to argue that you will not be downgrading your equipment to provide all those channels. The assessment becomes a question of whether you are looking for MORE sound or BETTER sound. Personally, my 2-channel system currently values around $10,000. This has taken me 20 years of periodic upgrades to assemble and is always waiting for the next available cash bundle to spring for that thing that's been bugging me.
Imaging is far better with a two-channel system. Good equipment will add soundstaging depth, width, and height that will make you forget where the speakers are in the room. This also works with a good DVD setup and good recording. No receiver on the planet will touch a two-channel pre/amp or good integrated in this regard. Go down to any good hi-fi shop and bring some music. Let them show you what you'll get for that money in your two scenarios. I'll bet my system it's no comparison.
My advise, get a good multi-format source, pre/power or quality integrated amp (see Unico Integrated, $1,500), and the best speakers you can with the money you have. Spend about $500-600 on cables. At this price point on a 2-channel rig, the cables will be audible. Don't bother with cables on the HT system. You'll need 2-3 times your budget to build a worthy HT setup that would be adequate as a music source. Monsters will serve just fine.
On the other hand, if you just need a lot of bass and something to show off to your friends, I'm sure the other posts will fill the bill.
Or, don't just trust my word, look at any audiophile publication and see where they spend their time.
klam