I have a 2 channel set up. What is the best way

An HT receiver is a good way to do this. You don't need a three chanel amp this way. Make sure the receiver also has inputs and outputs for the main channels.

With the receiver, if it has pre-outs for the main speakers, it's a bit different. You would keep your analog/music sources (CD, LP) connected to your integrated, and connect the video sources (DVD, SAT, VCR) thru the receiver. Run the L/R mains pre-outs from the receiver to an auxiliary input on the Rega. When you calibrate your HT surround levels, mark/memorize the volume setting on the Rega, and always return it to that position when listening/viewing material thru the receiver. You can do the same thing with a surround processor and external amp.

There are several integrateds available that offer theatre throughput. Most are, at worst, a performance peer to the Mira. On the cheap, a Classe CAP100 can solve your stereo listening and when combined with an older processor and a three channel amp will give you very nice results. My own system is a CAP150 with Marantz AV550 processor and Adcom 2535 three channel amp. Less than cutting edge for movies ... but more than sufficient to enjoy movies in your living room.

To Stbhorn, just to let you know about the receiver-preamp combo (in your case receiver-integrated) thing. On the cheap I did that for a year while saving up for a power amp 5 channel. Probably the only guy in the USA that ran an Audible Illusions 3 tube preamp into a Pioneer av receiver. You would be greatly surprised how good that receiver sounded when it was released from preamp duties and only had to pass power.

upgrade your 2 channel setup (spend the money there) and stay away from home theatre nonsense

Tom