Tube advice for MP 301 MK3

Hi everyone,

I have a little single ended 8wpc Musical Paradise MP 301 MK3 integrated. It's a fun little amp, but I've been running it with the stock tubes. I'm interested in trying some different tubes, but I'm pretty inexperienced on this. The amp lists the following as possible tubes:

Preamp Tubes:
6SJ7, 5693, 717A, 713A, 6SH7, 6SD7, 6J8P

Amp Tubes:
6P3P, 6L6, KT66, 5881, EL34, 6CA7, KT77, KT88, 6550

I was wondering if a seasoned tube veteran might be able to give me a suggestion or two on a higher quality tube that I'd be able to find without too much difficulty. Not looking for extremely expensive NOS tubes - just something that had a good reputation for great sound.

Thanks so much,
so i am no veteran perhaps but here is my 2 cents.. i have electro  harmonix. 6L6 and rca 6sj7 pre's. the black metal ones. the sound is flawless. no hum at all altho this may be true of any tube in this amp. the only upgrade i see is the kt 77 genalex offered on e bay for 40 a piece. from all reviews i have seen this is the best advice i can give you. fwiw, this is an AMAZING amp  for the money.