Need help fixing GMod server lag

So I have recently set up a GMod 32 Slot DarkRP server and once it gets around 20 players and beyond it starts to lag a lot and it can be quite irritating to play once the lag starts. There are 2x 64bit 2.8ghz Xeons dedicated to it and 8GB RAM with 2x 74GB 15,000RPM SCSI disks. All the addons on the server are:



Adv Duplicator
Combo-Fists
CSS Realistic Weapons 4.0 (Only the knife is installed)
daf (wasn't sure if it was needed for GMod but I have it on all of my CSS servers so I put it on)
DarkRP (latest SVN)
DurgzMod
keypad
keypad cracker
metamod
phx (latest SVN)
RiotShield
SourceMod (Only use it for SourceBans integration and have removed all unneeded addons from it)
ulib (latest SVN)
ulx (latest SVN)
wire (latest SVN)
wire model pack 1 (latest SVN)


My server.cfg is:



sv_lan 0
maxplayers 32

rp_showjob 1
rp_toolgun 1
rp_proppaying 1
rp_letters 1
rp_earthquakes 1
rp_maxcps 5
rp_drugpayamount 30
rp_maxdruglabs 4
rp_maxgangsters 5
rp_maxgundealers 2
rp_allowpdchief 1
rp_dm_autokick 0
rp_runspeed 400
rp_toolgun 1
rp_chiefjailpos 0
rp_voiceradius 1
rp_AdminsSpawnWithCopWeapons 0
rp_allowvehicleowning 0
rp_alltalk 0
rp_chiefjailpos 1
rp_chiefjailpos 0
rp_jailtimer 600
rp_restrictbuypistol 1 
rp_propcost 0
rp_earthquakes 0

sv_voiceenable
sv_alltalk 0

sv_maxcmdrate 66
sv_mincmdrate 33
sv_maxupdaterate 66
sv_minupdaterate 33
sv_maxrate 30000
sv_minrate 7500

mp_falldamage 1

decalfrequency 3

sv_logbans 1
sv_stats 1
log 1

sv_cheats 0

sv_downloadurl "http://trident-gaming.net/meow/garrysmod"
sv_allowdownload 1
sv_allowupload 1
net_maxfilesize 64

sbox_allownpcs 0
sbox_maxprops 30
sbox_maxragdolls 0
sbox_maxnpcs 0
sbox_maxballoons 0
sbox_maxeffects 0
sbox_maxdynamite 0
sbox_maxlamps 0
sbox_maxthrusters 5
sbox_maxwheels 4
sbox_plpldamage 0
sbox_playergod 0
sbox_maxhoverballs 0
sbox_maxvehicles 0
sbox_maxbuttons 5
sbox_maxturrets 0
sbox_noclip 0
sbox_godmode 0

sv_region 5
sv_timeout 65
fps_max 550
sv_stats 0
mp_timelimit 180


I have never set up a GMod server before but I have a lot of experience with other source games but unfortunately GMod is so different so it was no help and I have no clue what could be causing this. Any help is much appreciated! A $25USD reward will be given to the person who helps me fix this issue (Hope that isn’t against the rules if so I will remove it).

If you are hosting this from home, post the results from here: http://www.speedtest.net/

I am not hosting it from home it is in a data centre

I still haven’t been able to fix this… Does anyone have any ideas?

Bump.

You sure the server can handle that many people?

Yeah I have made sure that the server is able to hand that many people and that the CPUs are fine. After the latest GMod update things seem to be better but they still aren’t fantastic and how I want it to be. I have also been watching my CPUs very closely and neither of them have hit 100% usage…

What tickrate are you running at?

66

Try 75, it might improve it.

I thought servers could only use 33, 66 and 100