Raid 0 will give you the performance increase. however you will need to use drives of the same size and speed to get best results. (4x250gb in raid 0)
A big downside to raid 0 is the fact that if one of the 250's die then ALL of the data on all 4 of the drives is lost.
Raid 10 is a great idea but you will loose 50% of your storage capacity.
most basic & onboard raid controllers will only support raid modes 1 and 0
Raid 0 with 4x250 gb HDD's will probally give between 80-150mb/s read / write.
a single 128 or 256gb SSD will give easily 450mb/s read & write
all that being said. getting a single 128 or 256gb SSD will blow any raid setup with the drives you mentioned.