Over at diyaudio that has been a popular OPT for the tubelab SE amp along with the bigger CX version. Some use the 5K primary for less distortion at the expense of a little loss in output power. I would go for the GX for sure as it has had really positive reviews in that it sounds better to some than the CX. Price is nice too!
George Anderson of tubelab.com has a form @ diyaudio & you can look at a schematics for his affordable PCB's of his SE & SET amps. From what people say it, you might really like it! He was let go from Motorola a few yrs back and I think he want to get back to work, so maybe you two can talk & maybe you'll learn a lot about tube Hi FI !
For high end SE or SET George has used Electraprint a US maker that is popular for SE ones on the Forums. You are looking at about $150 ea. but depends on Wattage and Ma you will be running at , but may be more what your looking for and expect! Some have Golden Ears and it sounds like you will appreciate the higher quality ones!
Are you saying higher primary resistance than for max output power lower distortion? I have the other thread on this subject. If you have knowledge on this, please join in. I read it the opposite way that you use lower primary impedance to get lower distortion. I have no idea which is the right way. Please help.
For this particular SE amp, I am just trying to see whether I can salvage the kit amp as I spent $250 and it's a total garbage. Before I dump it, I just wonder whether I can spend like $100 to make it at least acceptable. I don't think my speakers are efficient enough, so I don't expect a lot. Just wonder any way to at least improve it a little. My money is going to be on the push pull tube amp as in the other thread where I am willing to spend the money. PP is going to be more in line with my speakers.
Thanks
Alan