UPGRADE TIME!! Preamp vs. Speakers???

Good day audio nutz!
this could be in Speakers OR preamps category but dont know how to post in both..?

I have one I would like your opinions in cracking...
I am considering upgrading either the speakers from Focal ARIA 948 to the new SOPRA n2 (after a demo) OR
upgrading my Simaudio preamp from 350p to the 740P.
The 2 Sim 400m monoblocs and W4S dac DSD SE  would remain.

My questions:
1. What would be the best "bang for buck"?
2. witch option do YOU think would be most noticeable?

I REALLY LOVE the Sim/ Focal sound so I want to stay in those brands I just want MORE of it..
things to consider I get about a 10% discount on gear
the speakers I would get full trade in cost of $5K
The 350P preamp I would get "most" back in the trade up program (plus 10% discount)

Ok let me have it!
and Thank you!
A good preamp can make a huge difference in the sound. Since you are buying from a dealer, I would audition the preamp and see if you hear a significant upgrade in your enjoyment of music. Don’t think about bang for the buck as much as what is going on musically and how you respond to it emotionally. I’m not saying the preamp is more important than the speakers, but I am saying that I think the preamp is overlooked by many audiophiles who maybe never really heard the differences a good preamp can bring.
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.