if you would be willing to wait long enough (4-6 months), I would go with a Low Down Sound cab. I was actually going to buy a MAG 410T (whatever version of the Ashdown cab was 4ohms), but I went into the store to try it out, and cranked it a little bit, and I found the cab actually farted out really early. Don at Low Down Sound makes some really, really great cabs for a really good price. I recently got my 4x10+6.5"/1x18 cab in, and I'm blown away by how great it sounds. the crazy thing is, I paid $900 after shipping for it. it handles more power than an Ampeg 8x10 (600 watts more), weighs 40lbs less, and cost $400 less than the Ampeg.
be aware there is a wait, but it's really high quality product that won't fail you. it's completely custom, and you control every aspect of the cab.
shoot Don an email and see what he would be able to quote you.
www.lowdownsound.com