Like most Rhea owners in this forum I too have had tube issues since the day I purchased it; however, I recently purchased a VTV tube characterizer that solved my problems. I have been able to go through old tubes and find nice matched pairs that work in V1/V2. The VTV immediately screens out noisy or microphonic tubes.
I also learned some things from the good folks at Aesthetix that can save you money.
V1/V2 require longplates which are expensive if you want NOS matched, balanced, quiet non microphonic. But it was explained to me that V1R/V2R work as a pair that needs to be matched to V1L/V2L. For example assume that V1R is 100/100 and V2R is 90/90. These two tubes could be matched with V1L at 98/92 and V2L at 92/98. If you add the gain you get 95 for each of the four triodes which is what you want. Remember V1R + V2R = V1L + V2L
I've also found you don't need to match the gain perfectly as in my example but just get it as close as your ear can tell. The tubes don't need to be perfectly balanced either but probably should be within 10%. They key is that they not be noisy. Nosiy tubes sound like wind and it's not tube rush because it varies in volume intensity. I have found that tubes that sounded slightly microphonic can work well too. More microphonic ones can sometimes be helped with a Herbies damper but really microphonic tubes ring when I touch the chassis.
Having said all that the Sovtek LPS are the quietest tubes I've tested so far. I got lucky with NOS tubes. I found some NOS early 50's Philips longplates that tested absolutely perfect as well as a few pairs of perfect Mullard 10M's, one pair of which is in V3 and the other in my Calypso. None of these NOS tubes were more quiet than the Sovteks but they were just about equal. I have some matched Brimar CV4004's in V4 and Philips 7308 SQ in V5.
I've had this setup for about a week now and I'm still pinching myself. After six months of one tube hassle after another some of which were of my own doing, I'm now in audio nirvana. The Philips tubes are 3D like. This is not the same Rhea I purchased. It sounds awesome now as opposed to great when it was working before. The noise is not an issue and I'm using an .24mv Airy at 68db balanced. It also works at 75db rca but it pops at 75db balanced. I'm not sure whether it's supposed to work at 75db balanced or not.
I wish I'd bought the VTV right away. It's expensive but it will pay for itself in the long.