On that date the forum was quite new with very less number of threads (maybe around 100-150) eventually very small database and 335 users were utilizing very less CPU resources and memory. Currently with over 26k posts the database is quite big having hundreds of persisting MYSQL connections with each user online. The cpu is now double and is optimized + tweaked quite well. Our current server is of Dual Opteron Processors/2GB memory and it can bear almost 5-10 times load than 335 online users. So there is nothing much you should be worried about
Current Server Specs:
Processor #1 Vendor: AuthenticAMD
Processor #1 Name: AMD Opteron(tm) Processor 248
Processor #1 speed: 2192.523 MHz
Processor #1 cache size: 1024 KB
Processor #2 Vendor: AuthenticAMD
Processor #2 Name: AMD Opteron(tm) Processor 248
Processor #2 speed: 2192.523 MHz
Processor #2 cache size: 1024 KB
Just for your information, if you are willing to buy one for your website, it will cost you around $400/month - $500/month