I have had my K-7 for 2 years and I seriously considered to upgrade earlier this year. Instead I bought some high-quality glass like FA31mm f1.8, FA*300mm f4.5 and a couple more. I have no regret and would do it again, because "
good glass is worth every penny" and "
good glass is an investment". (I may add that the strong Aussie dollar helped me to access lenses that would have been above my limits a few years ago...)
So,
I would go for the lenses especially since the K-x is still an excellent camera body.
Hope that the comments will assist...