Is there a cpu test for the firewall?

I am using look'n'stop with Phant0m rules on my 1.5 GHz T42. I am looking for an alternate firewall that is CPU light under heavy p2p traffic.
From http://www.matousec.com/, I found there are several free firewalls with excellent rating. However, I see no review on how they perform under p2p. Unfortunately, CPU is too short to be a keyword in this forum. Can anyone point me to a good discussion on CPU loading?

Online Armor, got it free today. Will try it later.
Comodo, I tried 2.x before. Heavy CPU loading.
Outpost Firewall Free 2009, I found in one post said it is a cpu black hole. Did it get improved?
Jetico, I tried it two years ago, not as light as LnS in my memory.
PCTools, someone said it is from LnS. Is it as light as LnS?

If you have tested all firewall recently, please share your experience. Thank you.

Edit: After reading "Did you choose your firewall according to Matousec ?", I found that what I really need is to add HIPS protection on my computer. Which is better? LnS + separate HIPS or firewall/HIPS suits? Again, CPU loading is an important factor to me.