well the express amps replaced the f series and i would agree that the f-50 would be a very good choice.
The express has many issues with some people on harmony central regarding it cant do the whole metal thing. Thats because the amp is very strange....it all depends on the guitar.
On my strat with a dimarzio tonezone..it gets pretty saturated and heavy. But on my yamaha guitar with a full humbucker jb junior it excels at all metal styles. There is more than enough chunk there for anyone in my opinion....it all depends on the guitar you use i guess....
.....best of luck and let us know what amp you do choose ya lucky git!!!