| One would wonder the best way to stat out a rival party. It may be too dangerous to actually roll up 5 PCs, but it should be obvious by now that even a group 3 or 4 levels higher can't really hope to match the PCs perfectly. I guess if you're planning on using them as a pile-on that's ok, but if you want them to be a persistent threat they need to be tough.
The initial guess at how to build a party would be to take the HP values of a party and try to find the monster level that roughly matches that, but don't forget that the PCs have healing surges to take advantage of. Perhaps a group of 5 elite "monsters" or 5 regular monsters with templates applied would give a good indication of what a party could be.
Imagine a band of shadar-kai against a level 5-7 party, and each shadar-kai has templates like bodyguard, champion, demagogue, or master of frost applied. This might be interesting. A fellow DM proposed this idea to me a while ago and I was somewhat washed by the idea that a party of adventurer's was common enough for them to bump into each other, but this is turning my gears. | 
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