Is this a good deal for the money?

Ah, i see.
But cogs are readily available up to 22t; both EAI and Surly cogs go up to 22t.
3:1 ratios are good gear wise, but will give you much fewer skid spots. But yeah, with a 41t chainring you've still got plenty of scope for running a spinny gear.

Oh 22t cool, and as you said 144bcd only go down to 42 tooth.

If I go for the stronglights, I'll just have to search around for a 42t chainring and something like 15 and 20 tooth cog. It's just all too much to figure out, I can't be fucked!!

Will your dropouts/track-ends and chain length accommodate such a change?

At worst I'll have to swap around the chain, which I shouldn't really do because of different amounts of wear on different chains and how they wear the cogs. I heard someone say that dropouts should be able to take something like a 3-4 tooth change in the cog. hopefully I didn't just make that up.