It is strange replying to my own post, but I have had time to experiment with a Line 6 Spider III 30, the Spartan version of the Spider III series 1x12.
I wish it was all good news, but after a week with the amp, it went back. I liked a few of the tones I dialed in, but the overall EQ response was shallow and not anything near the big, thumping tones of the Spider III 75 (most likely due to the smaller cabinet design of the 30). I kept telling myself that this is the 30 watt version and not to expect the same performance as the Spider III 75. However, the lack of an independent reverb, difficult to dial out shrill highs, and harsh distortion on the Boogie model forced me to return it and aim for something different.
For my next choice, see my post on the Behringer GMX210.