I think the main reason people have slowness issues with AC is that they aren't running it on a "Server" but rather a desktop or beef-ed up desktop. I sorta blame Amazing Carts for this, they try to tell you that you dont need anything special to keep the "costs" down. Well I think it simply isn't so. Spend the money on a decent server, with a server operating system, and you wont have any issues. It doesnt hurt with AC to also have a Gigabit network and if you have clients that are wireless (upgrade to wireless-n).
Sandeep has some good threads on making your own server, but if thats not your thing, I would just purchase a HP Proliant Server, With a Xeon processor, 6GB+ of memory, and 500GB+ of hard drive space (with RAID in a RAID 1 aka Mirror) so you would need two 500GB drives.
If you have questions and want to ask me directly about what I mentioned feel free to send me a message.
