#1
I'm pretty sure but want to make sure that this head:

http://www.orangeamps.com/products.asp?Action=View&ID=76

Is okay with this cab:

http://www.mesaboogie.com/Product_Info/Guitar%20Cabinets/ThreeQuarterCABS/TQ-1x12-LG.htm

Also I'm gonna get this cab for the head:

http://www.orangeamps.com/products.asp?Action=View&ID=86

Might sound dumb but it's a mates cab and this is the only decent amp head I've ever owned.
#2
Impedance and wattage-wise, the Mesa cab should be fine. The Orange cab is specifically built for use with Orange amps, so that should work even better.
Ibanez RGA121 | ESP LTD H-1000
Axe-FX Standard