VAC 30/70...pick your pre?

Good!

As a point of information, though, your Melody SP3 is a class AB amp, and the power it draws will therefore fluctuate with the dynamics of the music, and will be much less than 350 watts most of the time. While the power consumption of the class A biased LM SET amps will be essentially constant at all times.

What will be converted into heat by the LM amps will be the power it draws from the wall outlet (nominally 400 watts) minus the power it delivers to the speakers (which is likely to be just a few watts most of the time, or even less). It’s a different story with class AB amps.

Best regards,
-- Al

I will only have about 5 inches of breathing room up with the 219.

Hmm. Both amps are specified as consuming 400 watts of power. (Although I’m a bit surprised that the 219ia isn’t closer to something like 300 watts, or even a bit less). Nearly all of that power will be converted into heat, and radiated directly upward. Hopefully that space is open at both the rear and the front, and hopefully the material that is above the amps is heat resistant (and won’t conduct the heat into a component that may be above that surface). Otherwise, and possibly even given those conditions, I would have significant concern even with the 10 inches of clearance you would have with the 508ia.

Best regards,
-- Al

I’m imagining 92db and greater then if I want to use SET down the line?

Another factor that is equally important is that the speaker’s impedance should have relatively minimal variation as a function of frequency, or should be relatively high at all frequencies. Or both.

The Daedalus Ulysses that I use, and that a couple of others who have posted above use or have used (also with VAC Renaissance push-pull 300B amplifiers), have a 6 ohm impedance but combine an extraordinarily flat impedance curve with 97.5 db efficiency and high power handling capability. Which makes them exceptionally versatile with respect to amplifier selection. However I believe they cost upwards of $16K presently, if purchased new. Some of their smaller models, though, having a bit less efficiency and somewhat less deep bass extension, can be had new for something like half that amount.

The various Coincident models, one of which Charles uses, are also very versatile with respect to amplifier selection, and are certainly worth considering. As well as the relatively low priced (~$3K) Tekton Double Impact he mentioned, which in addition to being a remarkable bargain seems likely to be friendly to many SETs (especially those having relatively low output impedance), despite its 4 ohm nominal impedance. You may want to take a look at the current thread in which it is discussed extensively, and comments are provided by many ecstatic users:

https://forum.audiogon.com/discussions/tekton-double-impacts

Regards,
-- Al

Excellent comments by the others.

A caveat regarding the possibility you mentioned of combining a CJ ET3 with the VAC amps. Like many CJ preamps the ET3 has very high line stage gain, 25 db in this case. My perception has been that the unspecified gain of my VAC 70/70 is also somewhat high, especially in its zero feedback setting which I and most others seem to prefer (although that will be speaker-dependent). And I would presume the 30/70 is similar in that respect. While I suspect that the resulting overall gain would be ok with your vinyl source and 87 db speakers, you mentioned that you are considering eventually adding a digital source, and upgrading your speakers. The combination of a digital source, higher efficiency speakers, and the high gains of those two components would be likely to result in having to use the volume control on the CJ preamp undesirably close to the bottom of its range.

I’ll mention also that for a few years I used a Classe CP-60 solid state line stage preamp with my VAC 70/70, and I was happy with the combo. I purchased the CP-60 here in 2008 for only $1350.

Good luck. Regards,
-- Al