Bukkit server not utilizing all rescources

Well first the info:

OS: Debian Linux 5.0
Architecture: 64 bit
Java:
java version "1.6.0_22"
Java(TM) SE Runtime Environment (build 1.6.0_22-b04)
Java HotSpot(TM) 64-Bit Server VM (build 17.1-b03, mixed mode)
Wrappers: No wrappers besides my 3 line script that auto-restarts the server
Build: 953

The problem:

I run the command java -Xincgc -Xms2300M -Xmx2500M -jar craftbukkit.jar nogui on my 2.5GB RAM vps to start my server. It works relatively well but it seems rather laggy even if there are only a few people on. When I use the top command the process is always using 50-55% cpu, and starts using 29% memory and gets up to 60%. Even when there is the maximum 25 people on the server it uses 60% memory. I've tried just setting -Xms and no -Xmx, tried different values of -Xms/-Xmx, used just java -jar and tried -Xincgc on and off. The server generally crashes every 2-4 hours, which is why I made it auto restart. Generally it is an OutOfMemory exception. Is there a way to force bukkit/java to use all the memory?

Plugins:
PanelMaster, CraftBookMechanisms, CraftBookVehicles, VoxelMore, WorldEdit, Permissions, CraftBookCircuits, InventorySort, Tips, CraftBookCommon, iConomy, Essentials, VanishNoPickup, WorldGuard, SimpleSave, CreativeGates, EssentialsSpawn

Thank you.

 

no so that means your map is too big or u will have to get rid of some of your plugns

 

Gee thanks for spamming a bunch of replies and adding your server in your sig. Anyways...