what is my system's weakest link?

Bottom line is how much do you like the THiels and want to invest in getting the most out of them. AN amp upgrade would be the initial solution.

Focal is a good option to consider. They are much easier to drive than Thiel in most cases, and I tend to think of the two as being in the same general sound quality camp when things are going well. Worth considering. Triangle (also French like Focal and also generally much easier to drive than Thiel as well) would be another.

I see that the consensus seems to be that the speakers should be the first to go, I have to say that they would be my least preferred component to switch out, mainly because they fit beautifully in my space, which might not be able to accommodate every speaker, and though its superficial I really like the way they look, I have to say that the exterior of gear is quite important to me (and to my wife :)..) + speakers are hassle to have shipped to you etc.. oh and I think the sound great I mean I never thought they would be the main reason why my system isnt all it could be..

I guess thats why I felt prone to getting a new pre and power.. instead of the brio or perhaps getting a new cartridge for the TT or a new table altogether.. very confusing times.. hard to figure out what sould go :)..

During my crazy days of changing equipment almost as regularly as my underwear I owned a pair of Thiel 1.6s. They were only a little larger than the 1.5s but they were so much better to my ear. Much smoother sound with deeper bass. Also much better looking IMO. You can find them for less than $1k used if you watch.
I still prefer the sound of the Vandersteen 1c in that size and price.
All of my searching was an attempt to better the sound of my old Meadowlark Audio Kestrels. My quest seemed to focus on time coherent speakers such as Thiels and Vandersteen. There are a lot of nice options out there but I gave up searching a couple years ago.

I don't think there is a consensus to change speakers.

Moreytalmor, this is a perfect example of why it's important to give as much detailed and concise information as possible when asking for opinions on this forum. First of all, remember that these are just opinions (ours) and it's yours that count to the most. However, without all the facts we are forced to read between the lines. For example: THE ONLY comment in your post re the kind of sound you like was the reference to the Mc preamp as being "warm". OK, I figured, the guy wants a warmer sound. Reinforcing that assumption was what I know about the sound of the Thiels; they are not what I would call warm. Now we learn that not only do you think they sound great, but you like the way they look and seem to be reluctant to give them up. That's great, and nothing wrong with liking the way gear looks. OK, if they sound great then that tells me that the amp/speaker synergy is probably not too bad for your listening habits and tastes (notice I am still reading between the lines).

So, what areas exactly are you feeling the sound of your system is deficient on? What are you looking for? More fullness (warmth), more detail, bigger soundstage, more volume? Or are you looking for simply an overall, general improvement in sound from "great" to really great. Also, does your budget of $1300 include the proceeds from the sale of whatever it is you end up selling? What cartridge do you have on your tt?