Hi mate,
I'll be honest: I've been entirely focussed on completing the Mod Database thingy for the past week and it's pretty much consumed all of my attention (Sharon hasn't been best pleased about it, let's put it that way
)
Off the top of my head, though, I'd be reluctant to use the website you suggested just because it's a third party one and would be much more susceptible to downtime. I can't even remember if someone said that Sony offered an official PSN card solution or not - don't suppose you know, do you?