More cores = less php execution time?
 

My current system is a hosted 2 gb ram (mysql db is 1.5 gb). 1 core cpu. My system now does have sufficient speed. I wonder what happens if I upgrade from a one core cpu to a dual core cpu with 4 gb RAM while all other variables stay the same. vBulletins debug mode tells me that mysql outputs pages within less than 0.0x seconds where php takes more than 0.3 seconds.

1. The more ram does not give me more speed as I currently have more than enough?
2. Upgrading to a dual core cpu will reduce php execution time. Will it be half of the original time - then 0.15 seconds?