Number of Digium PCI cards in one box

Hello All,
I am trying to figure out how many Wildcard TDM400P one can install into a computer without causing any issues like noise and echo. I have a setup where I need to connect 8 outside lines to VOIP server and then connect three analong phones to VOIP server. So basically, I will need to install 2 TDM400P with FXO modules and 1 TDM400P with FXO module. Now some consultant told me that there is a limitation where I can only install two TDM400P PCI cards. If I install the third card, it will create number of issues related to voice quality.
Is it true? Even if I have independent IRQ assigned to each of three cards? Any help or pointer to get more information about this concern is appreciated.

-= harp

I think you meant two with FXO and one with FXS? In any event, I don’t know of any such limitation, but if you have that many inbound lines, is it more cost effective to bundle them into a PRI?

You might also look at the 2400p card that will give you plenty of room for expansion