Hi!
AFAIK all *recent* A1s are using 933 MHz CPU (as 800 MHz ones were not available), but as the Board (especially cooling) is designed for a 800 MHz CPU it is clocked at 800 MHz. You might modify the cooling (adding an appropriate cooler for example) and then clock it to 933 MHz yourselves, though. Maybe the US-Dealers did this already ?
(Myselves I still have my A1 clocked at 800 MHz, though it is also using a 933 MHz CPU, and it is NOT an US one which I bought BTW).
BTW: If you find the A1 offers too expensive, there is the possibility that you only buy the A1 Motherboard at your Amiga dealer and put together "the system yourselves", like those PC guys usually do... especially if you add only an
older GFX Card (let's say Voodoo 3) you will get the system MUCH cheaper. And a cheap PC case (there are really cool ones too).
Also components like GFX Boards, SCSI Adapters and Soundboards are very cheap on eBay !!!
You can get an A1 (without monitor, I guess most people have already a fitting monitor

) for below 1000 EUR (around 1000 USD) this way. And you still can buy a Radeon later and add it

Of course if you feel unsure about putting together your own system it is probably best to go for one of the "complete" offers.
Steffen