Recommended Equipment
-----------
Center: A PAIR of two-way, two-driver (1 tweeter, 1 woofer) fairly small magnetically shielded bookshelf speakers that have bass-reflex and twice the impedance of your reciever as well as half the wattage of the rest of your speakers (you'll see why later).
Corners: Four IDENTICAL two or three way speakers that are significantly (preferably 3-4 times) bigger than your center bookshelf speaker pair. I recommend NOT using bass relfex speakers for corners.
Subs: If doing a 7.pseudo 2, you are going to want two identical powered sub woofers. Front fire, downfire, and reflex towers all do something cool so it's really a personal preference on what types to get.
Side channels: You'll need a decent sound chair or you'll have to modify an existing chair to have speakers.
Placement
-------
Center:
Depending on monitor size, you'll want to either place your cetner pair either to the sides of your monitor, or if possible directly under it. The more you spread them, the more you'll have to turn them to face you. You'll also want the tweeters to be at ear-level. The cetner speaker pair will be closer to you (except maybe the sub) that any other speaker.
Corners:
Ideally, you'll want the corners at EQUAL distance from where you are sitting. Depending on the spread of them you may chose to make them face each other directly or aim them at you. If you can not place them equally then you'll have to balance them out with your volume control so that they all sound equally loud. The tweeters should also sit several inches HIGHER than the ones that are on your center pair.
Sides:
Sides are easiest to implement with the use of a speaker chair. You'll want the chair to be capable of it's own 2.1 so that the side channels share the same bass source. Try to find one that doesn't suck and use that for your side channels by hooking it directly into the side out of your sound card.
Subs: If you choose to use bass reflex towers then you will want to place the each sub with the ports facing your rear speakers to the sides of you in between the front and rear channels. If you choose front fire subs then you will want to place them slightly in front and to the sides of you and have them facing you directly. If you choose downfire, then you will just want place them to the sides of you between planes of your side channels and corner channels.
Wiring
---
Center Pair: Your two speakers will need to be hooked up in PARALLEL. To do this, run a set of wires of EQUAL length from each speaker to your center output on your reciever.
Corners: Regardless of where you place your speakers, you will need to use THE EXACT SAME LENGTH OF WIRE FOR ALL YOUR CORNERS.
Illustration
Equipment this was done with:
Receiver: Sherwood RD 6500, 5.1, 100 watts per channel, 6 ohms (can handle 4-8)
Corners: ESS HD 308 Speakers 200 watts max, 2 way, 5 inch horn tweeters, 8 inch woofers, 8 ohms
Center: Pioneer S-HF21 pair 100 watts max (each, together they can handle 200), 2 way, 1 inch semi dome tweeter, 5 inch woofers, 8 ohms (each, 4 in parallel)
Sides: HEAVILY modified Pyramat 2.1; 2 side drivers in head rest, one sub mounted on back
Subs: 8 inch no-name drivers place inside enclosures and set in a down fire configuration