Signal tube versus power tube, sound impact?

In my experience with my Decware amp, it’s finding the right combination of tubes that is the key. The stock tubes that came with mine were really good. Then I started experimenting with different combinations and since I had several of each type, I ended up with 12 different possible solutions. 
 

In the end, I found that a ~1960 vintage Telefunken signal tube and generic Russian $28 power tubes were the best sounding.

Usually power tubes first then signal tubes in an amp. Also it’s the first signal tube in the series for a particular channel that has the most impact. For instance, if you have 3 -12 ax7s  for each channel, the first one in the series has the most sound impact, the others less and less as you go to the last tube in the series. 

Amperex Bugle Boy

f your amps are running 12au7’s the Amperex Bugle Boy tubes placed in the central "gain" positions can be very good. However, buyer beware as I have heard these are sometimes Asian fakes. The two linked above look almost too good to be true - usually the vintage tubes show wear to the Bugle Boy logo. If these are real, they look exceptional.

Lot's of good suggestions here, although overall maybe a bit confusing/overwhelming (no surprise).

Personally I've had good outcomes with the front (small) then back (power) strategy, other than one KT150 based amp as there are no other options besides Tung-Sol. In this case replacing the stock JJ pre-amp tubes with some NOS Telefunken Diamond Mark Red Tips worked magic. 

I have not been impressed with GL KT88 tubes vs. JJ. I returned the GLs. This was in my first tube integrated - a LineMagnetic.

A trusted source is important and I have mostly used Brent Jesse at audiotubes.com. Everything he has is listed on his website, and he gives good advice without being pushy or overselling, and has a very reasonable return policy.  

Although expensive, if you want to warm things up, the NOS Mullards are pretty special and currently in my tube DAC - however, and this is where Brent Jesse comes in - I have some 1950's GE long plates (branded as Wurlitzer) that I rotate in and out of the DAC that sound remarkably good in the DAC at 1/4 the price.