Can I substitute a 12AU7WA for a 12AU7 in a Primalina amp?

Yes! The WA is a military grade tube.

WA is always a better grade tubes, surely you have to try 

In this modern era of tube fakery, nothing means anything, in my opinion. However there is no electrical difference between a 12AU7WA and a 12AU7. Tubes labeled ECC82 would also be acceptable. This is to say that you could pop any of these tubes into the same socket and be confident you have done no harm.

Thank you gentlemen, your input is greatly appreciated!

for your pre amp, would suggest you get the PSVANE 12AU7s and the PSVANE 5u4G rectifiers for your preamp. will really open up.