Mixing yeast brands

I recently ordered ingredients for a DFH 90 minute IPA clone and I was planning on brewing this week. I ordered everything I needed including a pack of Wyeast 1098.

I use Mr. Malty to calculate pitching rates, and with a OG of 1.085 it says I need 2 packs of liquid yeast and a 1.5 liter starter. I've never ventured in the higher gravities before so I want to make sure I did this one right. I stopped by a home brew store 2 hours away while visiting family this weekend and picked up a second pack of Wyeast 1098 for the starter.

I got an email today saying they were out of the Wyeast 1098 that I ordered, but would replace with WLP007. Should I wait until they get the right stuff back in stock? Use the one pack of 1098 with a step up starter? Or make a starter of the two yeasts mixed together? Is mixing yeast strains a bad idea? They look pretty similar....

If you're making a starter, why would you need two packs of liquid yeast?

You'll be fine. You can either step up with your starter (which will be cheaper) or mix the yeasts. There's no problem with mixing yeasts. (In fact, you can get quite creative with it.)

I accidentally mixed 1056 and 1098 in a batch of APA. It seemed to accent the hops but flocculate well (a trait that 1056 lacks). I have kept reusing it. Anyway, if you aren't going to make a starter, mix away...