I've been looking into the possibility as well.
The complete kit looks like the safest way to go, something like £650 so not too much for the performance on offer.

The kit includes the DSP (frequency correction) unit but there is an analogue filter unit that can be used instead, designed by Nelson Pass. This would be my choice and reportedly gives identical performance.
You do need two quality stereo power amps as well, recommended minimum power of 80W for the bass and 25W for the treble.

I'm tempted..