I have used a1x12 and 1x15. Both sounded great. I have sold the 1x12 cab now and use a custom 2x12 but only using 1 speaker for steel the other is for my second quilter for guitar. The amp runs on 4 or 8ohms.
Mullen Custom Discovery, Quilter Mach 3 with Celestion bn-300s, Peavey Nashville 112 with Celestion bn-300s, Telonics Multi taper, Lehle Mono 90, Zoom MS70, Peterson Strobostomp. .