1. No... generally RAM compatibility is just the motherboard doesn't work with the RAM, the ASUS board will probably work with more kits seeing as there don't seem to be any complaints of RAM issues so far.
2. This looks good - the OCZ Reaper CL6 1600 MHz kit for £82.99 including VAT.http://www.overclockers.co.uk/showproduct.php?prodid=MY-201-OC&groupid=701&catid=8&subcat=1517
3. I don't think it would suffer RAM issues, but I'm not sure what other good boards with the same feature set would be available.