Id probably sell my ENGL Screamer combo (and Z5 footswitch) if asked, i really need some cash and due to a change in family circumstances i'm NEVER home in a position to actually use it properly, so i'm using my Guitarport mostly.
It wont give you a Mesa tone as its not a Mesa, but it does metal very well, and for the money i dont think you will easily beat it.. of course, you might hate it.. but there you go :)
Id stay clear from an Ashdown FA...
I had a 40w (non DSP) one, the gain without a boost was 'ok' at best. The amps are aimed at a bass heavy 'nu-metal' sound.
They get very, very hot which can melt various plastic bits\glue and cause problems, i think the newer ones are better (mine had a fan on it which added noise.. but at least it didnt melt!!!!).. its not that its a BAD amp, just voiced strange and a tad unreliable, and you (imo) should be looking at something more versatile and more reliable, saving for the amp is one thing, repairing it is another headache!
Over the years i've had alot of gear, and realised one thing: its nice in theory to aim at 'sounds' on cds, but those sounds are tweaked and tweaked and recorded by pros and engineered, so you will only ever get 'pretty close'. At one point i had a JCM 800, sd-1 pedal and a LP with EMG 81s as i was a huge Zakk Wylde fan..didnt sound anything like him (or play like him!) and ditched the amp as being too limiting.
Its hard to explain... but imo a good sound is a good sound, so i can play metallica, maiden, ozzy etc on any amp that i can get a good metal sound from..they sound like they do, i sound like me playing their stuff (probaly makes NO sense lol) ;)
Hard choice though... decisions decisions!