How to upgrade B&W Matrix Series 2

The upgrade frame-of-mind is starting to set in and I am considering upgrades to the B&W Matrix Series 2 speakers, purchased new in the late 1980s. Unfortunately, the only local dealers are midfi at best although there is a Vandersteen dealer within a 90 minute drive. The amplification components are all Pass/Threshold with the S550e amp and Fet 10e preamp and Sony SCD 777ES CD player. I think the speakers still carry a good trade-in value. The budget could probably accomodate new speakers in the list price range of $4,000 or so and then I would work to trade or sell the 801's. Auditioning in my location is difficult, so I am searching for opinions which can make my search a little more efficient. Thanks.
Is there anything in particular you like or dislike about the 801s? The big compromise in those speakers was the crossover, which I recall prompted some aftermarket mods (JPS Magic Flutes, others) which some felt were solid improvements; if you still like the speakers you could seek advice from people who got those mods, they might be worth keeping.

If you want new speakers, though, it would help others here to find out your listening biases; the 801s were very good at telling you what your sources were doing, as opposed to more forgiving, or "musical", speakers like the Duntech Princesses I bought at the time over the 801s. The new B&W's are quite good in the mold of the 801s, but they are expensive, and to get them in your price range you might be giving up a good deal of bass--does that matter to you over the same or better resolution? Or do you want a less revealing speaker?
Those are good refinements to my query. I do like accuarcy in speakers and it is true the 801's let me know what is in front of them. I would not like to give up the bass which i now there. Rock is not my music but classical, jazz, and good vocal recordings are. To my ears the Threshold amplification is very good, though I may add a tube preamp at some point. It may be that improvements without five-figure list prices are hard to achieve.
Well, I'm not familiar enough with a lot of the newer speakers out there from smaller companies, but given your tastes and amplification I'd think that you might want to figure a way to audition some of the larger (3.6 and up) Thiel speakers, which need the power your Threshold can deliver, or a used pair of Dunlavy SC-IVAs or Alethas. Used these speakers would be in your price range. In addition, VMPS speakers might be an alternative if there's a way for you to find them, although I haven't heard them for years. They seem to be still made and from the reports quite good. Revel and Snell are two more brands that might interest you, although I haven't heard them. Finally, you might want to see if the B&W N804s deliver enough bass for your appetitite. It's tough for me to come up with speakers that can satisfy your criteria, as quite frankly the 801s are still excellent speakers and to get their level of resolution and bass extension today is likely to be expensive; in addition, since I'm a tube guy, I'm not sure how your amp would sound with most of today's speakers, although I would not consider it a weak link by any means. Hopefully some other members will have suggestions for you.
One other suggestion--perhaps the Vienna Acoustics Beethovens, which may be around your price range. I heard them sound surprisingly good with a large Krell home theater amp in a lousy acoustical environment, particularly with classical music. Most of the Vienna Acoustics speakers I've heard probably have a slightly sweet, maybe rolled off, high end, but they might work very well with your Threshold. Far more and better quality bass than I would have expected from a comparatively small enclosure, and very musical.
The 801 upgrades from North Creek may be an alternative. They are around $1600 and the web site, as one would expect, certainly makes them seem attractive. I wonder if anyone has any experience with them. Thanks again for the comments.
Maybe North Creek has some referrals, as many of the modifiers do? Or you can start a new thread to find out more about them. It certainly would be a cost-effective way of improving a speaker you obviously seem to enjoy. Good luck!
I have two pair of 801c series 2 and one has the North Creek crossovers. They are being driven by Classic 150 amps that have had cap upgrades done at Audio Research. The crossovers greatly improve the overl performance of the speakers. The bass is more solid and the mid-range has gained detail and musicality. I like experimenting with new possibilities, but the cost of upgrading on the performance of these 10 year old speakers would be substantial.
My 2 cents... I have just upgraded from 802 series 3 to a USED pair of Thiel CS6. WOW!!!! Maybe not as good as Vandersteen (which I was going to buy) but I got them for $4500.00.