I have a Mesa Diesel 1X15 and I love it. Excellent cabinet. It's a friggin' TANK. Casters are your friend. Not sure about the pricing on the 4X10 or 1X18, but I've seen 1X15 cabs go for 250-300 bucks. I honestly don't think I've seen a 1X18 cab. I'd be all over both of those.
Ibanez SR300DXL, Mesa MPulse 360, Peavy VT 410, Mesa Diesel 115, Digitech BP355, Beer, More Beer...