amp-preamp considerations.

In many cases, you will lose the tube benefits by forgoing the chance to use a tube pre.
As for heat concerns, tube preamps use small tubes and generate very little heat compared to tube power amps. Almost all have the tubes inside a chasis.
Premier 14 is older, but also nice.
If you are dead set on a solid state pre, check out the pass labs and classe. Still think this isn't the way to go.

Well, this is a unique experience for me - recommending a SS preamp, but what the hell.....If I had to buy one, and I didn't need a remote, I'd get a used Threshold FET10HL (designed by Nelson Pass, by the way when he owned Threshold). I've seen them sell on Audiogon for about $750+/- and you can't get even close to this value at that price, new or used, IMHO. By the way, what are you looking for in a preamp and whats your budget? New or used?

Conrad-Johnson Premier 18LS?

Well it is not as easy to just buy a preamp or an amp, it comes down to synergy. For example, my friend has a Carver amp and he happened to mate it with the Musical Fidelity 308 preamp, funny but they just click together, why because what the Carver lacks in the mid range the MF adds to the mid range and they kind of work well togehter, go figure. To make your system the most musical, you hae to mate strengths and weaknesses together.

My 2 cents and Happy Listening.

Of the pre's you mentioned either the pass or as someone else mentioned the CJ premier 18. However, In my opinion you would have been better off with a tube pre and ss amp for which there are many more synergistic matches. Tube amps require more maintenance and are more costly to maintain not the mention the heat issues. In my experience you get most of the tube sound from a tube pre-amp. This is why it is so important to pick the right tube pre-amp. The tube amp is more icing on the cake more inner detail if you will; usually at the cost of bass control.

I have a tube pre with ss amp and love the combo as many on this site have commented and or experienced. However, I love tube amps and I am probably going to purchase a tube amp (CJ premier 140)to replace my MF2500A. Having said all that; I still believe your best sounding solution as well as equipment synergy would be a tube pre-amp like a CJ premier 17/16. In my opinion anything less would compromise the premier 140 and you do not want to do that. Again, just my experience and opinion. Happy listening and by the way great purchase.