New tubes or new preamp?


I have an ARC LS15, and am considering either a set of NOS Amperex tubes, or selling it and getting a new preamp, such as an ARC LS27, or a Modwright LS 38.5.
As I'm unable to compare , what would you advise?.Will NOS tubes give me a preamp that compares with todays current ones, or is it a waste of money?
Thanks
brrgrr
"I put a NAD C162 pre-amp into this system (not my main system). It's my back-up pre-amp. The NAD is full sounding with good bass."

Did you leave the SP-9MKIII powered on all the time? If you did not leave it powered on you never heard it. So now you think the OP should dump his Audio Research preamp and get an NAD?

BTW, AR is Acoustic Research.
Rrog says: "Did you leave the SP-9MKIII powered on all the time? If you did not leave it powered on you never heard it. So now you think the OP should dump his Audio Research preamp and get an NAD?"

I have had the ARC SP-9MKIII in 3 of my systems and listened to it in 2 of my brothers reference systems. I'm pretty familiar with how it sounds. I also have a ARC LS-2 and a Cary SLP-98 to compare it too. Oh and I guess the old NAD and another pre. Anyway, in the wrong system it can sound a little dry. I'm thinking that is the OPs problem.
I never recommended the NAD, I told him to borrow a different pre-amp and try it out. The synergy with the ARC pre-amp wasn't there in my system, maybe your system is not like mine and you have different results. I'm just passing on my results, if you don't find that useful, for your system, then maybe we both learned something.

Thanx, Russ
I've been running direct from my Oppo 105 for a bit, as I returned the tubes ARC sent , and just have an old set of Sovteks that are not good, to say the least. Will have to get a decent set of tubes so I can sell the LS15 in good conscience, and give it a listen at the same time....speakers are starting to settle in and the sound has improved recently...just need to decide on a preamp....will probably try to get a used one and , if it doesn't do the tick, resell t and try something else...the joys of no decent local dealers!..