[Asterisk-Users] what hardware to choose from?

[Nguyen]

Hi list,
I am ready to implement VoIP for 2 of our offices. i do like to setup
asterisk box in each office (behind PBX) and use our ADSL links to provide
the tunnel. This will provide cheap telephone calls between offices.

I also like to setting PBX, so it can let incoming call-thourgh to asterisk
extensions, so our home users can use office * box to call to other office.

I don't want to completely upgrade the old equipments ( phones, PBX, etc..),
part because the cost, other reason is we have tied too much to POTS in most
of our life.

What I am confusing about is which hardwares I can choose ? There are lot of
things:

Gateways :              Antek VSP-5004 ( www.antek.com.tw) , D-LINK 1120,
Multitech,...
Telephony card:     Quicknet LineJack, Digium,  Dialogic, etc...

Those gateways seem to have loaded with lot of features : FXO , Ethernet,
NAT, QoS, various codec 723, 729 AB, SIP, H.323, ... and the price (for
those made in Taiwan ) is low.

The telephony cards are interfacing well with PSTN and PBX (in the past, we
used Dialogic D-41D to provide IVR and voice mail services). But I don't
know how they are interfacing with IP network. And configure a box with 4
cards can be much higher price than use a gateways.

But I see that a lot of people on this list using telephony cards. Can you
tell me, is this a personal habbit or there are hidden pros of    telephony
cards that I don't know about?

And what I should choose for our project : gateways or cards?

Any comments is greatly appreciated.

Best regards,
Nguyen