Thanks all, for your comments and insight.
Yes I'm running my Cornwalls with my SEX amp, flea powered as it may be. I think the combination is stunning. I've been wanting to build a SET using 300b's or 45's, or maybe even 2A3's for quite a while. So when a nice pair of 45's became available I thought I'd go for it.
I think I'm going to like it fine, what's the worse that can happen, right?