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-

My opinion is that the Center channel must match your right and left channels to sound "seamless". Rears don't matter as much and can be added in the future. A subwoofer helps more than you know. Not only does it have a dedicated track on almost any movie, when you don't use a sub your main speakers have to handle this load. Movies have a ton of wattage draining bass. Your overall sound will improve by adding a sub.

You will need a preamp/processor. These can be configured for anything from 2 speakers up to full surround. Most will allow you to start with 2.0, 2.1, 3.1 or more (.1 is the sub).

Your computer and DAC can continue to be used as a source, ie CD Player. Blueray players vary greatly. One with streaming is great if you like to rent movies on-line. The only other issue is HDMI. Older pre/pro's don't have it. If you are going with a new tv, new dvd/blueray, this should be a must.

Lastly, add a pair of rear speakers when you like. They can be powered to match your fronts or just run from a little power amp.

Thanks everyone. So it seems I will need to dump my Wavelength Crimson and get a pre/dac with a HT bypass if I am to combine my current 2 channel mains into home theater duty. Aside from Emotiva gear (thanks for the suggestions), any other recommendations for pre/dac with HT bypass?