Will 2 watts monoblock 45 tube amp work for 90db speakers ?

think I would be looking for speakers in the 94-98 db eff range for use with a 45 SET amp....they are really about 1.5 watts, 2 watts is pushing them pretty hard.

Actually 1.5 watts is about double what you traditionally get out of a 45.  You really do need speakers that are more efficient. I ran some old full range speakers that were rated 99dB with my 45 SETs in my bedroom- and that was volume challenged- they sounded loud not because they were but simply due to those higher ordered harmonics I mentioned earlier. The ear uses those to sense sound pressure, so when the amp makes them it sounds louder than it really is. The problem is, it doesn't sound as nice when it does that.

I've heard Ralph from Atmasphere say that you don't want to push tube amps to the higher end of their output range as their sound quality begins to suffer, so you may want to consider that as you search for an appropriate tube amp.

To clarify this- the statement above is true of all amps, but in the case of SETs the higher ordered harmonic distortions start to show up at about 20% of full power, so if you really want to hear what the amp does you need a speaker that allows you to run the SET with all forms of music at power levels less than 20%... in the case of a type 45 based SET, that means a speaker that is about 105dB or so at a minimum in most rooms.