First off you are missing one in with that bunch QTelNet … they are in the same class, but dont have digital gateways.
Multitech : Way too expensive ($1100 for 2 ports) , requires static IP to avoid any down time, firware can be updated remotely, free tech support
QTelNet : best bang for the buck ($575 for 2 ports), can use DHCP or static and no down time if IP changes (big pro for me) , remote config and upgrade of firmware, free tech support
Cisco : Solid product, very expensive as you require a call manager, you pay for tech support. They dont sell stand alone gateways like the others.
Quintum : A200 is crap, digital gateways are nice but pricy, you pay for tech support, Static IP needed to avoid down time.
Noname is right you should go digital and get a partial PRI the levels will be better, but you will pay for this.
Example only :
8 non digtal line $160-200 mth
4 QTelNet FXO $2300 US side
4 QTelNet FXS $2300 India side
Partial PRI $500-800 mth
Quintum D800 $4000 (approx)
Quintum or other non digital gateways in India