The Tubes are available at www.upscaleaudio.com, I think they were around $20 each. They have a whole lot more if you want tho spend $$$. As far as increased soundstage, I think all of the upgrades, tubes and cables, made a contribution to the sound quality. I had the tubes recommended to me by Matt, the guy who makes the Cableplex cables. I am not familiar with the PS Audio, but for the money I think you will not regret anything from Cableplex. I have an Audiophile uncle who just upgraded his entire HT, and His daughters HT, to the cableplex Nirvana cables. This includes a special subwoofer cable.
As you can tell, I can't say enough about the cables, this is my personal opinion and the biggest enhancement to my system.
Good luck with your decisions
As you can tell, I can't say enough about the cables, this is my personal opinion and the biggest enhancement to my system.
Good luck with your decisions