Best performance setup for vbseo ?

we have a dedicated server we require suggestions on installing software for vbulletin + vbseo.

Server config:
Dual Processor Dual Core Intel Woodcrest 5140
4 Total 2.33 GHz Cores
Dual 1333 MHz Front-side Bus (FSB)
4 MB Shared L2 Cache
2 GB 667 MHz FB-DIMM Memory (Fully Buffered)
2 x 250 GB SATA HD in Hardware RAID 1

We have around 1500 users/guests/memebers online any time on a 10 min cookie timeout

We have forums which use vbseo + do not use vbseo

Maximum users/guests/members during peak hours goes to 2500 .

What version of mysql, php and apache needs to be installed?

Best chaching software (apc, eaccelerator, xcache, etc.)

How should be compile/install mysql php and apache ?

Is there any sequence to install/compile apache, mysql and php ?

I meant should we install php or apache or mysql first for best performance ?

If you donot use any panel i strongly advise you to use lighttpd or nginx instead of apache I would go with nginx , php 5.2.6 mysql latest verson and xcache as php caching.
In any case your server have a lot of CPU power but you are lacking ram. You shall add at least 2 gb more ram. Also you may consider replacing your hdd's with a raid setup and faster rpm hdd's

looking for appropriate answers ?