In reply to BigLob:
It's a great trek. I hired a porter from Nepal Eco Adventure who were a good company. I also booked the Lukla flights through them which was helpful because their guides from other groups helped me a bit with the flights.
$50 is a bit excessive for food and drink, I think I spent closer to $20 per day but it could be done cheaper (I enjoyed some cokes, beers, and chocolate bars in the higher up villages).
Hopefully you can do both, but if there's a choice between Kala Patar and EBC then do Kala Patar - the view, particularly of Everest, is spectacular. I assume you'll also get to do Gokyo Ri? There are great views and it's good for acclimatisation before the Cho-La pass.