Ok, here it goes...
I've heard you front end on Maxx's with Halcro using Transparent Reference XL cabling and it was one of the top 3 systems I've ever heard. So your front end is not lacking Depth.
In Response to Cellorover - No the WP7's aren't at their limits!
We need to know your cabling (the comments about the norst are what I heard and are not a good match for Wilson with the amplifiers I've heard), power conditioning, and Room treatment.
I've heard WP7's on VTL 450 monoblocks with VTL 7.5 preamp and Burmester front end with all transparent Reference Speaker cable and power conditioning.. truly amazing
I've heard the Sophia with VTL 5.5 preamp, VTL stereo 150, and Transparent Super xl cabling with Acram cd player (you could hear the limits of the CD players resolution)
I own WP7's and I have tried a ton of amplification setups.. Rowland 201's (amazingly smooth but need some more current (not watts), can't wait to try the 501's), EAD Powermaster 2000 (warm and very pleasing with a huge soundstage), Currently I run LAMM M1.1s which are truly amazing! I've owned Music Reference RM9's, ARC Solid-state (D400MkII, D300) and tube amps, SIM (Yuk!) Sumo (thin and dry), Listened to Levinson and Classe (thin and dry on top) most bi-polar (versus mosfet) on Wilson make them over analytical (not pleasing), I have used a CJ Premier 14 preamp which was amazing except for it couldn't handle the 5 volt output from my Gamut CD player, I have had a placette Active Preamp (This was the first preamp that truly amazed me and transformed my system) So I compromised on the Rowland Syngery IIi preamp because it was 95% of the smoothness of the CJ, but with 30% more bass than the placette (which was huge already), and coupled to my LAMM amps my system is liquid but imaging suffer because of acoustics! 4 pieces of Sonex and two tube traps improved imaging/layering by 50%, or my old Argent Lens (which I regret selling) made a huge difference.
The Pass equipment would be a good match also but needs to be run with balanced cables to fully utilize the potential and to minimize ground problems (X250 should be enough -actually runs higher in class A power than the X350)
So if you haven't treated your room at all (especially the first order reflection points you will never achieve your goal with equipment changes) I will be contracting Rives Audio to fix my room and more importantly make it look good (the hardest part)
Secondly like other posters pointed out cabling is crucial to establishing system synergy! I have found that Transparent (with XL tech, or the newer MM (warmer)) improved my system even more so than a single component change. Truely amazing (you need to try Super or higher to get these effects with your Wilson). I bought some PS Audio Statement interconnects XLR because of some reviews (they are only 20% the cost of mine) but they delivered BOOMY bass and a forward presence (sitting in row 3) but the soundstage collapsed to only between the speakers and the depth died completely and there was no layering front to back... very disappointing (100+ hours break-in time) they sounded good for rock except it was harsh on top(yuk). But I learned that balanced on my preamp and CD player did improve the attack, so I have bought balanced Reference Interconnects that I am picking up from my dealer tomorrow. Cardas cables were too dark. Anything with Silver was to bright and not defined, Kimber was boring, Audioquest was pointless (couldn't hear a difference as I went up the line??), MIT is on my video system but I feel Transparent betters MIT in every aspect, except in price.
I don't think you need to quickly make a preamp step but ..
The ARC preamp's are more like Solid State versus the tube warmth of say an CJ Premier 14, 16 MkII. Those ARC's prefer balanced cables and the Lamm is single ended. I almost bought a Lamm preamp but I can't live without a remote but they will sound amazing and the build quality is amazing. Consider a Rowland also if you want something in between the ARC and the CJ, but I really thing you need to look at the rest of your system (post it!) before you start switching out things.... (i even went back to stock power cables because the high end Electroglide cables I have added too much detail and texture (made me dissect the music instead of listening to it).
Your Wilsons came with an excellent manual, grab a friend, mark you speaker position with painters tape and remove the spikes and put a doubled up towel underneath and start following the steps to setup your speakers. It is definitely easy but takes 2 people and some time over a couple of days.
After I do the acoustics, I will spend more time spiking my speakers and pulling the frisk off.
Good luck and enjoy (there is tons of potential in your WP7's)
