The online option is for those in today's society that don't carry cash or even use a checkbook, which is happening more and more. It's not required, just another way to enable people to bring their tithes and offerings.

I've never heard the pastor make the statement that the Old Testament is not relevant.

Regarding volume, the balcony - as well as the back rows - are recommended for those that desire less volume. I've attended services at a church that seated 7,000+ and that was much closer to concert volume than what Berean does.