Thanks Russell

Certainly not a mile away, it is precisely what I'm trying to achieve. The big difference in my plan is it is just for fun but primarily I will be doing it on the cheap. Essentially I will take a USB feed from a computer and go into a cheap multi-channel DAC (stuff they use everyday in gaming rigs) and from there to a multi-channel amp. From there I will take 3 stereo pairs and drive the 3-way drivers in Goodmans Magnum K2s. Within the computer there will be a digital cross-over such that the feed to the DAC will have 3 stereo pairs. That is the first step.

As a second step, assuming the first step is fine, I will do room correction via REW (as per your link) and a mic. As I understand it REW will create a FIR filter which I can inject into my software.

Looking at my costs (I consider the computer, software, multi-channel amp, cabling and speakers free as I already have them) the biggest cost will actually be the banana plugs, binding posts and DAC. That should be about £100 - so a cheap(ish) experiment. Not sure what I will do with it all once I have done it as my main system are more than adequate.