Tube Pre and Solid Amp

I wonder if tube pre must match with tube amp. How about tube pre and solid amp? I look into this question from the point of system reliability. I think the latest best solid amp can reproduce 95% of best tube amp. So a solid amp is a better subsitution for tube amp in terms of reliability, duability, maintenance free, isn't it?

I have a Krell PAM-3/KSA50. A pretty old solid combination. I am considering upgrade it with VAC tube preamp and Pass Labs XA160. Hope this will get somewhere I enjoy the warm and musical sound of tube and the punch, power and above mentioned advantages of solid. Any comment.
I am using an Eastern Electric Mini Max tube pre driving a Spectron Musician II digital amp. I have listened to a Pass X350 in my system. It was a tough decision because the Spectron sounded so much more to my liking. The Pass had killer looks.

I have had 28 different amps in the past 12 years. This combo is the best.
Any combination of gear has the potential to sound good. There are many many members here who can attest to this. There are even those with a solid state pre and tube amp.

Your question gets asked about twice a week, so you can also search the old threads.

I think you will find that "maintenance free" and durability is not a criteria most audiophiles use when choosing gear, although we do like good factory warranties.
Check previous threads
I am currently using tube Audio Research Reference 2 MKI with SS Pass Aleph 2. They are working pretty well. Both gears are sweet, smooth and warm. The only weakness from Aleph 2 that I can think about is the bass control. However, I use a Genesis G-500 active woofer speakers to make up my weakness. I am also thinking about to upgrade my power amp and speakers to Pass XA160/XA200 and Cello Master Strad (passive) in the future. In my opinion, the tube preamp + SS power amp combo is the best way to get the warm/sweet tube sound and also maintain a good bass control.
What would be the short and log run problem if unmatched impedance between tube preamp and solid amp?

To what tolerance is acceptable?
I have been using a CAT Sig pre-amp with GE smooth plates and a Rowland Model 8 amp (ss) for several years. The combo is truly a great match. I used to have a tube amp ( a Melos) but the heat, reliablity, and the concern about where on the tube life cycle you were at was a real downer.Plus here in S.Cal, the main issue is the amount of heat that the tube amp puts out. The Rowland runs mildly hot but not unbearable. To me the heat problem is a major factor.
Since the 1960s, all equipment are designed within similar spec where impedance matching wouldn't be an issue any more. It's rarely to see preamp and amp have impedance matching issue.