KEF Reference 4s - anyone using these?

Attention KEF reference owners - please help!

I came across a couple deals on the big KEFs that I couldn't pass up so I did a no-no - bought speakers without hearing them. I've just received a set of KEF Reference 4, the KEF 34D surrounds and a pair of Reference 2's for the rear if I decide to do EX (which I think is a bit gimicky). Front end is a Marantz SR-14EX with the new Pioneer DV 38A. I will do both HT, 2 channel listening, and maybe even DVD-Audio.

Has anyone used the Reference 4 for serious 2 channel? For home theatre? Which sub is a good match (am considering REL Stadium, Velodyne HGS 15 or 18, or M&K 5000 MKII - but would be interested if someone has experience with 2 smaller subs vs. one 15" or 18". (I know the sub won't be neccessary for 2 channel given the bass reputation of the Ref 4s.)

The Marantz is 140 x5 , will biamping the front 2 channels help? If so, should I biamp the centre also (a KEF C200). and with which monoblocks. Or should I just sell the Marantz and go with something like a Sunfire Signature (can't afford Krell or Levinson)

Room is large 23 x 22 x 10 and somewhat problematic shape wise. And finally, I need to run decent speaker cables to the REf 4s(retail $600-700 is my limit for 6-8" Biwired Pair.). For the back pair (for DVD A audio) what can I get away with since I can't afford anything too high end considering this is 18' foot run (am considering Kimber TC).

Sorry for all the questions -- want to get it right -- Lorne
I have KEF Reference 105/3's for mains (same as 4's but with 8 inch woofers instead of 10 inch woofers), KEF 200C center channel, and Velodyne HGS-12 sub. The KEF's, IMHO, are good for 2-channel listening ........ great imaging and soundstage. You do have to watch the bass, there can be quite a bit of it and you have to get them away from the walls ........ but when you do they sound good ....... you have a large enough room so this shouldn't be a problem. The HGS-12 has been a great sub .... very tight and clean sound. My room is smaller than yours, but from what I've heard and read, the HGS-15 should do the trick for you ..... and I think better than the M&K will do (IMHO). I've heard it takes a bit more power to run the newer KEF Reference speakers than my older ones. I can tell you that the better the equipment, the better you'll like your KEF's. I started out with an Acurus A-250 and have moved up to a Llano 300S (300 wpc class A amp) and there is quite a difference. My guess is that the Acurus would've been better power than your Marantz receiver .... so you can read into that. I'd go separates ........ I had a receiver and went to separates and noticed a lot of difference. If you get a good high-powered amp, you shouldn't have to bi-amp ........ but one always can depending on how far you want to go with things. Good Luck.
Thanks for the advice! looks like I should dump the Marantz and go separates as soon as I can -- which is what I expected, given the size of these Kefs.