Based on my experience with the Merlin VSM-MMs and B&W Nautilus 801, 802, 805s, I'd recommend the Merlin TSM-MM or MX. Note, the TSM (and VSM) have been upgraded to either the TSM-MM or TSM-MX (premium) status. I personally found my merlin VSM-MMs greatly outperformed the B&W 801, 802, and especially 805 except for the last bit of bass extension that the 801 provided. (That being said the VSM's bass was much cleaner). The MM and MX versions or upgrades are SIGNIFICANT improvements over the TSM-m or vsm-m. In fact, Bobby Palkovic (the designer/owner of merlin music) stated the TSM-MX outperforms the VSM-m floorstander, which is amazing. The MM and MX upgrades or new speakers improve upon the previous M version in all areas, such as bass response, imaging, soundstaging, smooth highs, defined lows, etc., AND they mate, much, much better with solid state gear. Even if you decide to go with the TSM-Ms, these will IMHO still outperform the sig 805s by a fairly large margin. You can always upgrade them at a later date.
Having heard most of the nautilus series, I feel that the merlin TSM-M/MM/MXs are the way to go. You can always call Bobby P. at merlin, and he can give you advice about equipment selection, setup, room treatment, etc. even if you are buying used speakers or decide to go with the B&Ws. No matter what your pricerange is, if you decide you want to upgrade your gear, bobby can give you tons of advice. He is so accessable and friendly, you really should consider giving him a call. I'd strongly suggest trying to demo the Merlins, as I think if you do, you won't give the sig 805s much more thought. Also, as has been mentioned, check out audioreview for the ~60 5/5 ratings for the VSMs and ~ 40 5/5 ratings for the TSMs, including several people who switched from sig 805s to tsms.
Jason
