If you want to use for sending calls to PSTN from IP, the easiest way is to simply set the lampattern to the incoming digit pattern, like if you are receiving cc+number, set the lampattern to just the cc.
Then if you need to add a 0 to the front of the number, you would need to set the lamreplacment to 0. Also you will want to setup answer supervision.
As for SIP, keep in mind that the SIP software for the A800 is only Beta. Quintum will not be producing any further software for the A800 as it has already reached its end of life as a product from quintum and no further software will be done for it. If the beta works, then good, otherwise if it does not work, quintum will not fix it. Also, beta means that quintum has not tested the software fully.
These are just precautions you need to know.
If you switch to SIP, then the A800 will only do SIP meaning it will not support both H323 and SIP at the same time, nor on call-by-call.
I know with the time difference it may be difficult to get together to discuss further, it may be easier to just send me an email directly (firstname.lastname@example.org) instead of constantly checking this forum.
Also, I should be online on Saturday in the morning my time (NY time).