I too would recommend Andy, assuming you are going the NOS route. He will not only know your unit, but can make recommendations based on the sound you like. Tubes that sound good in some manufacturers' products will not necessarily sound the same in another's, that's part of the reason Andy is so good. Another reason is that anything you buy from him, though pricey, will be the real deal and will have been thoroughly tested.
If you want to go with current tubes and not the pricey stuff, if you still own that ARC SP3 and that's what you're talking about, I'd suggest asking ARC.
If you want to go with current tubes and not the pricey stuff, if you still own that ARC SP3 and that's what you're talking about, I'd suggest asking ARC.