asterisk users - Jan 2007 - AsteriskNow - H323 support for trunks

First of all, I was wondering if this is the right place to post 
questions and issues around AsteriskNow.
If so, here's my question:

I've been using Iphonecom.com's services for abour 3-4years now, to 
connect and call my brother who lives in the US and my parents, sister 
and me (all located in Belgium).
We're OK with their services, but we wanted to be more free in 
call-numbers, options, ... So I decided to give Asterisk a go, and try 
to host these things myself (dedicated dsl line, dedicated server, ...) 
That way, we could also use my landline here to let my brother use the 
belgian phone system to call other relatives and friends, 
after-working-hours, which is free overhere. (for me that is).

Now, Iphonecom.com only uses H323 as they mentioned 'they have too many 
problems with SIP thus sticking with H323 for the moment to guarantee 
everyone's service'...
I was wondering if I can use this account in my Service Providers tab, 
and connect through my account, and receive my brothers call, before 
migrating him over to my Asterisk system. Just as a test-scenario...

Anyone tried or did this before, pref'd with AsteriskNow. My knowledge 
about asterisk (especially configging) is rather basic, but I'm willing 
to learn ;)

Thanks people!
Great product, great user-base support!
Love it!!!

Bram