UPGRADE TIME!! Preamp vs. Speakers???

I might start by taking my preamp and amp to this dealer and compare my preamp to the preamp I am considering as an upgrade using the speakers I am considering as an upgrade.

Great Info and thanks for the responses so far,
To address a couple of your comments..
I couldn't agree MORE about upgrading both (way way down the road I likley will. but funds are a bit short for both speaker and preamp at same time.

Ricred1: Sim 350 p and 2 400m monoblocks are already seperates:)
all interconnects are fairly high-end as well.

since finding out the purdy new Focal are just sort of 14K that is not even remotely an option (looks like they will be my next used speaker buy)

I think i will have to sit around and wait for a used 740P to come up.

Mesch: I will be demoing the preamp soon! where I can compare with MY speakers/ and the rest in my house.

While there is merit to the "weakest link" argument in general, I do think that where speakers are part of the discussion that argument is less likely to apply, as long as your amp is able to adequately power your speakers. 

In my experience, speakers are almost always your best bang-for-the-buck upgrade and changing speakers will impact your sound more than any other component, where the change will be less significant or to as great a degree. 

Tho certainly audition to see for yourself if at all possible. 

Turn the whole thing off and walk away as it's all nothing but trouble. 

I can't comment on the difference for the speaker upgrade, but I can comment on adding a 740P to my system.   I used both  a Pass XP10 and Hegel P20 with my Pass X250.8 amp before getting a 740P preamp and the enjoyment of my system jumped up significantly.   More so than I would have imagined considering the other two preamps are great for their MSRPs.   If you factor in the MSRP of the 740P and the fact that my DAC and many others sound great direct, the $$ spent for the preamp (basically just a volume control in my case) may not be the best value.   But in relative terms to upgrades I've had in my system with respect to electronics and pricey cables, the 740P certainly was worth the price.    The depth and space around the instruments and vocals with the 740P in the system is pretty impressive and I know I would greatly miss it.