Cheap reliable 100 wpc tube amps

I wouldn't wait. If you are careful in your selection you will have no difficulty in reselling it later if and when you decide to upgrade. For example, I'm still using in a 2nd system a Sonic Frontiers SFS 80 I bought 10 years ago - you can buy these on AG for less than $1000. They are built like a tank, easy to use, and with the right tubes are very tuneful, and a bargain compared to what you get for the same money new. There are other brands as well.........

Be careful about a couple of items when buying older tube amps of this power:
1-hum can be a real problem. Older caps will go
2-Make sure they can handle the impedance of your speakers? Some older amps won't go for less than 8ohms.
3-check out what kind of tubes are in them or that they need. Good KT-88's can set you back a bundle if you have to retube. If the sellor doesn't have a tube tester and can't give values, I usually figure that it will need retubed sooner than later.
4-A lot of people pay extra for the name, ie MacIntosh. Don't let that sway you too much. A newer Rogue or Quicksilver may work better in the long run.

I have the luxery of having a good used audio store nearby. I was able to try some of these cheaper tube amps without too much sacrifice. My experience has been with the older, cheaper arc's and cj's and dynaco's is that they have more of the shortcomings and less of the strenghts of going tube, and are much more sensitive to matching speakers. Depending on what you are used to with your ss system, you may not get anywhere at all as far as enjoying an improvment, which takes the fun out of choosing tubes and maintaining the amps, which is a big part of going tube. (or MUCH bigger for older amps).
On the other hand, if you are willing to put in the effort, sometimes these super-low priced bargains can be made to sound surprisingly good and far exceed what is reasonable for the cost, but this takes more misses than successes.
I offer this further advice- take note that evan the more expensive tube amps require attention to system matching to have them perform the way everyone raves about when they recommend them. I would pay close attention to the speakers you are going to use and the preamp before getting any tube amp, and then you will be rewarded with the benifits of going tube.