It's up to you. Two ways to look at it. You probably own the closest sounding amp that exists to the VH4. (The VH2 isn't technically out yet). So, you aren't gaining a whole lot really. But, on the other hand you also have an amp with a nearly identical power section to a VH4, so your Hagen with the preamp bypassed and the VH4 pedal probably sounds as close to an actual VH4 as one can get.
I personally would pass. I've owned the Hagen/Herbert/VH4 all at the same time playing them all back to back through the same cab. The VH4 and Hagen are not that far off one another, VH4 is just a bit brighter and a bit more aggressive. I'm also not a pedal guy. I'd rather just buy the amp, rather than buying something that emulates said amp. But, a lot of people like pedals so my opinion isn't worth much. Good luck.