No, he needs to save his money for the Ref. 3, periods, commas, etc. . . are a luxury he can do without.
You can do easily exactly what you are trying to accomplish where you are running both preamps (the MX 135 and the Ref. 3) into the same amplifiers (assuming it has two inputs (ie. one balanced and one single ended) and is auto sensing between single ended v. balanced. Under this scenario, the risk is that you can only be sending a signal from one preamp at a time (if you mistakenly send signals from both preamps into the amp at the same time - you will not like the results).
So the question is - if you are the only person who would ever turn on the Ref. 3 and you don't leave it on so that somebody can come along and turn on the Mac Pre, then you can do this with a higher degree of confidence.
I have two kids and a wife and I would not feel comfortable with this. You can of course use the HT bypass of the Ref. 3, but I believe you are correct in that in HT bypass, the tubes are active in the Ref. 3. There are other good tubed pre-amps that allow you to not power up the stereo preamp when in HT mode - Cary in particular. However, in my opinion, the Ref. 3 is a better preamp than the Cary preamps - but that is a matter of personal taste.