How do I do it?

I have a 2 channel setup, which I love and want to keep as is: computer, DAC/Pre, powered speakers. The plan is to put a big TV on the wall and add home theater to the room.

Preferably, I'd like to incorporate the 2 powered speakers as the mains: L, R channels in the home theater setup, instead of purchasing new front channel speakers. But also want to be able to continue to use them in the 2 channel system.

I understand I need 3-5 more speakers, but what else do I need? How do I proceed? Thanks..
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. 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!

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...

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?
If I understand your situation, I think it is a little more complicated than you think.

Sounds like your PC has a digital output and the output of a HT receiver will be analog. So, you are trying to connect a digital connection to a DAC/pre-amp and also to connect an analog signal from your HT receiver to your DAC/pre. That means your DAC/pre-amp needs to have switchable inputs between a digital input and a analog input and the analog input needs to be a HT bypass. There are not that many of those units out there. I am not an Emotiva expert, but I do not think their DACs have an analog HT bypass. Their analog 2 channel pre-amps do, but they do not have a digital input, because they are not DACs. Correct me if I am wrong.

The typical setup takes the analog output of a DAC and the analog output of a HT receiver and feeds them to an analog pre-ap with HT bypass for the HT. You could do that in your case but then you really want 2 bypass loops in your analog pre-amp if you want to maintain a pure path for your Crimson.

An alternative is to take the analog output from your DAC and pass it to a HT receiver and use a Direct mode on your receiver. That does however, put some of the receiver pre-amp circuitry (like the volume control) into the signal path.

I think you are going to have a challege unless you incorporate a 2 channel analog pre-amp into the solution.

There are some 2 channel pre-amps with both digital and analog inputs and HT bypass. Classe, for example, has one but at a much higher price. I am sure there are others, they just are not that common.

I think you need to slow down and look at what it takes to integrate 2 channel digital and analog signals and HT bypass into one pre.

I think I got this right, but if not I am happy to be corrected.