How do I do it?

IMO if your 2 channel system is properly setup, you don't need the added speakers. The added gear, expense and trouble doesn't warrant the benefit. The benefit is having two speakers behind your head.

For a 2 channel HT system the only additional gear you may need is a processor to decode the TV signal and convert it to analog. If you have cable box with analog outs you don't even need it, as you can take the signal from the box.

Do not listen to those who poo-poo a multi-channel setup. When done properly, it sounds fantastic and does things that systems with only two speakers can dream about.

You need two preamps/preprocessors. The 2-channel preamp needs to have a home theater bypass. Then you need a multi-channel preprocessor. Emotiva.com makes both of these products: XSP-1 or USP-1 for the 2-channel side. They also make the UMC-200 multi-channel preprocessor.

Additionally, you'll also need either powered (active speakers) or some passive speakers. Then, a 3-5 channel power amp to power the speakers if you use passives. Lots of folks make amps like this. And I can vouch for the quality of the Emotiva amps. Their XPA-3 or XPA-5 or UPA-500 would fit the bill. Just decide on the power you need and make an order.

Finally, you'll want a subwoofer. SVS, Velodyne, Rythmik, and many, many others make very good subs, you'll need to do some homework.

Good Luck!

-RW-

FYI, there are some Gallo A'Divas with stands for sale right here on A'gon. And he's asking only $499 for the pair, a very good price. These would be exceptional rear channel speakers...

http://app.audiogon.com/listings/monitors-anthony-gallo-a-diva-ti-silver-with-stands-2013-08-28-speakers-94061

-RW-