Dedicated Small Run Envelope Printer Help

I run a wedding stationery business and print a lot of short runs of envelopes. I'm looking for an affordable solution for printing envelopes.

I have a HP 4200 with a the envelope feeder. It actually works really well for what I need it to do, except on some types of envelopes it appears that the fuser isn't quite hot enough for it.

I also have a OKI C711 printer and while it prints nicely, it can only feed 3 envelopes at a time, so I end up have to babysit it.

Does anyone have any suggestions on a good envelope printer for me. I generally print on a heavy weight stock (either plain or metallic), and all 4-bars, a2 or a7.

Thanks in advance!

 

I should also add that I came across this http://www.feedstraight.com/speciality.html and it peaked my interest. Has anyone used this/heard of it? Would it work with a OKI c711?