Yep...I'm with Bolero on the pot size. I mostly use those tall, skinny pots for my paphs. The pots are only big enough for one year's growth and I do repot them every year. Oh, and when I get new ones...I repot them immediately regardless of bloom...never had a problem.
I've used the SHultz mix in the past and it'll be fine for your new paph. If you're not great about keeping an eye on the moisture (like me) you might want to add a little chopped sphag to that mix for better moisture retention. Remember...they don't want to be soggy but in the words of our very own Kevin..."gently moist".
BTW Kevin...every time I water/check my paphs I can "hear" you saying that in my head..."gently moist". Don't know why but it's stuck in my brain and it won't leave.