I have used a PH7 in my system and done a bit tube rolling with it. The stock Sovteks tend to be quiet but they can sound a bit mechanical vs NOS. The whole 6DJ8/6922/7308 family is open to you and what to use comes down to personal preference. A reasonable 'middle of the road' place to start might be 7308 Amperex Orange globes. I've also had nice results from using 1 Valvo + 1 Siemens 7308 per channel, also 6DJ8 Telefunkens. Matched pairs (3-5%) for each channel will give better results, but super tight matching (1-2%) is not absolutely required. Most importantly, you'll want whatever you choose to be *quiet* with no or minimal microphonics. Have fun tube rolling your PH5!
Tim
Tim