It's hard to know what an SX32 would currently be worth as I've not seen any for sale in some time. Prices of most Amiga hardware has really been dropping in the past year, with the exception of 060 and PPC accelerators which have been shooting up in price due to AmigaOS4.

There is currently an SX-1 on ebay currently at £0.99 here. So maybe watch that to see what it ends at.

But there is also someone on EAB offering a MK1 SX32 at the moment here. And it doesn't look like it has been sold yet.

And maybe post a wanted advert on Amibay.