Tube advice

Nothing wrong with tubes from Tube Depot. Pay for matched sets. The trick is knowing how to bias an ARC amp, especially the VT series. You have to bias your amp(s) and you should be doing this often as they will shift as the tubes age. Before you temp to bias your amps be sure you know what you are doing or you'll have big problems. You might want to post this on the amps preamps forum. What ARC amps do you own? Do your research on how to bias your amps. If you post what models you have I'm sure many ARC users will help you out. If you're going to own several tube amps you should invest in a tube tester. There are plenty of junk tube testers out there so do your research and find one that's been gone through and calibrated. Good luck

marktomaras - yes your ARC amp will in time drop out of bias; the VT100 is not a self biasing amp... double check but I'm pretty sure it's not. I know the VT50 is not and my dad checks his often and checks his tubes as well on his tube tester's.

moryoga - your preamps are simple. Your Ref 75 is another animal but as you mentioned easy to bias over older ARC amps. I agree probably best to buy from ARC on your Ref 75. For your preamps I have had great luck buying tubes from Cryoset Certified. I'm not sure if you can bias your preamps manually as I would guess they are self biasing but not sure. You have some very nice equipment - I'd invest in a tube tester. Not sure how people with tubes survive without one unless they have a friend or shop close by.

ARC VT 50, 100 MK I, II and VT200 amps are difficult to bias. If you don't have highly matched tubes it is almost impossible to bias one of these which likely you will if you're lucky only lose a tube and a resistor in the process. If you're not knowledgeable on basic electronics, know how to read a schematic and comfortable with a soldering iron I suggest not tackling one of these amps as you'll likely send it in to ARC to get it fix. The VT100 is a great amp and this is the reason they're on the used market so often, or were several years back. For what it will cost to send a VT100 in to ARC to get retubed and biased by them you couldn't buy a new amp for the money to replace it. If you don't know what you are doing I'd send it in to ARC. 

lewm and marktomaras you might want to read up on this. 

http://mycollins.net/audio/artube1.html

As far as a tube tester goes I bet Upscale Audio and ARC use a tester before they send out tubes so saying a tester isn't an important necessity for a tube user is questionable especially if one likes to roll tubes often. I agree to keep track of your hours but a tester does much more than just test the strength of a tube. Just curious if you own a tester - lewn? The driver tubes in an ARC VT100 do require biasing I believe.