Hey Chris,
Yup, more times than not there's always a trade off...

Have a set of Tungstram ECC-82's which when ran at 5ma sound amazingly transparent and dynamic, literally perfect.
Apart from increased hiss.
Knock the bias current back to 4ma, hiss drops a lot...but so does the "magic".

Some brand new valves to roll in, my other ones are NOS and have a fair amount of time on them, so will see what happens.

The JJ 12AU7 pair are thought very highly with other guys with the same pre-amp, so fingers crossed.
Glad to hear your experience of Attenuators, that was maybe a road I was going to go down.
The higher value resistor is a good shout from Alan, in the queue if different valves don't sort it.

TBH unless I put the ECC-82s in at 5ma, all other combo's are liveable, but want that magic without the hiss - if possible!