Never played through an Express but I have used my JS1000 with three different Boogie amps.
1) Mark IV: Absolutely blistering on the lead channels with the FRED engaged. Didn't do much riffing (it wasn't my amp), but riffing would sound good with the p/u's in the middle or bridge position (the PAF pro in the neck tends to get muddy on its own).
2) Roadster: I owned this amp for a while. Sparkled in the clean channels...but I never found that the recto crunch matched well for this guitar. The JS p/u's are designed to be very "open" sounding, which never mixed well with the recto...in my opinion.
3) Stiletto Deuce II: I currently own this amp. Best all around match for all p/u positions of the guitar with all channels and modes on the amplifier. Riffing sounds good and the leads smoke.
Hopefully this is of some help. I never found the JS guitars to have a great bass response for heavy metal riffing..it always sounds a little thin, so keep this in mind when you're playing the amp. You may need a more focused p/u in the neck position to help out with this.