what brand of tubes to buy?

Have a parasound hca1200 amp,a friend has put a darad 2007 special edition SL2000a tube pre in my hands to play with. It came with 2 sets of tubes (china 12at7) which sound great on hard rock( base pressures that make my eyes pulsate at just above normal listening levels LOL) and a set os sylvanias that are beautiful for acoustic jazz and the like.I can see why people roll tubes but short of buying every brand and experimenting(and spending stupid money)how do I make choices on brands and what differences should I expect? Obviously new to tubes,but blown away by the improvement over ss pres.any advice would be greatly appreated!
Stanman is your friend just letting you use this piece of gear? I only ask because it wouldn't make to much sense to buy your friend new tubes unless you really like him. I wish I had more friends like you.

Here is a link to an article that talks about this pre-amp. http://www.stereotimes.com/amp040306.shtml

If it is now yours and wanting to play "roll tubes" the choices are very personal and it's hard to say what you will like. I have never used the rectifier used in this unit. But here are my personal opinions on the 12at7. Remember they are my own and other peoples will differ.

I like the German best. I currently use Siemens E81cc in my amp and Valvo 12at7wa in my pre-amp.

The British tubes are nice and have good midrange but seem a little too polite in my opinion. I have Mullard CV4024 and Brimar CV 4024.

I feel the stock Shuguangs are not bad tubes for the price.

Jan Philips 12at7's are not a bad tube and can be had pretty cheap. A bit romantic and slightly rolled off but still darn nice.

Haven't tried any others
Detredwings sums it up nicely.
Thanks for the input, ya he's trying to intice me,and the sob did just that!LOL the sonics and sound quality ie: detail,and presense is intense. Did not think this amp and speakers (vintage 92 epi 150/2/3 were capable of such sound preasures and detail, also have some old polk (80's I think) rta-12b's to try.but I've been converted! Do intend to buy the pre, price and value seem very good to me. I know there vintage pres out there that are better but price and value is right for my 1st dip into the tube" pool" it seems to match up nicely with the parasound and the speakers so I don't have to invest in any new speakers, at this time LOL. Guess I'm going to have to play around cause I like such a wide array of music types. Thanks oh so and others welcome to coment.
Got some siemens from b.jessie and wow,just increadable.saving for telefunkin "what the hell" gone this far might as well go all the way! Thanks for all the insight
Congratulations Stanman, you’re a quick study. I’ve been into tube amps much longer than tube rolling. Now, I regard it as essential; something that you realized in week one. Brent Jessie is a terrific supplier. Andy at Vintage tube Services is another.
Ya I wish I could do the same with speakers!stuck with 3 set of MAIN speakers! I now have to "roll" speakers too!!! LOL just can't deside which is best. Truth is they all are best, just different.
Don't ya just love this "hobby"