Thanks, FRM! Just ordered 4 and am awaiting total with shipping.
Don't know if I recounted my experience with buying 24 6H23n tubes for under $5 a pop IIRC (about $20 each from US vendors). Got the box and tested them immediately. Production dates were all over the map but the early 70's ones are awesome. Got two nice strong quads, a few lesser testing pairs that are close and two outright duds. All in all quite happy with the results. Looking forward to hearing the 1578 Melz's.