Too many connections?

[Azurel]

Hello.

I see in MRTG that connections are limited to ~1000 and page load time is from time to time slow (php is fast).

http://picload.org/image/cccorlp/mrtg2015-01a.png

httpd.conf:

Timeout 60
KeepAlive On
KeepAliveTimeout 5
MaxKeepAliveRequests 80

<IfModule prefork.c>
StartServers 8
MinSpareServers 5
MaxSpareServers 20
ServerLimit 750
MaxClients 750
MaxRequestsPerChild 4000
</IfModule>

I increase values with:

Timeout 60
KeepAlive On
KeepAliveTimeout 5
MaxKeepAliveRequests 256

<IfModule mpm_prefork_module>
StartServers 50
MinSpareServers 25
MaxSpareServers 50
ServerLimit 512
MaxClients 512
MaxRequestsPerChild 10000
</IfModule>

and get in MRTG this output

http://picload.org/image/cccorlw/mrtg2015-01b.png

Limit still exists, but processes now a little higher. I use latest Plesk 11.5 version with nginx on centOS6 with 32GB RAM. Is my actual prefork setting wrong or is something with NGINX wrong? Can anybody help me here, please? How I can get more connections or stopping slow page load time?

# free -m
total used free shared buffers cached
Mem: 32105 31605 499 38 1921 24803
-/+ buffers/cache: 4879 27225
Swap: 999 0 999