Guilt-inducing purchases

Who would have thought buying a car seat would cause so much angst? Each time I have bought one I've felt guilty over trying to save money on a cheap one -- as if by cutting costs I'm a bad parent. This is crazy, I know, but I still think it!
Today I bought (well, laybuyed because I couldn't carry them) two seats from Target. The first for Baby G is a Highpod Madrid convertible. I plan to keep him rear-facing until he is 12kg. He will go in this seat when I return the capsule next month. I also bought a Highpod Barcelona. This is wear the pain begins.
The Barcelona was the recommended booster on the Choice site and I thought it would be great for LB in J's car (she's in a Safe and Sound Maxirider in my/the family car). But, and it's a big but, when I got home I realised it is just a booster to use with the lapsash, not a seat like the Maxirider with a harness. There's been heaps of press lately about two girls who died in car accidents when strapped in with adult seatbelts and the talk is that the laws will be changed to keep kids in a child restraint with 5-point harness until around 4 and then in a booster with a H harness until seven or so.
Doh! This means I should probably replace the Barcelona with one with a harness. Not too big a problem, I'll just exchange them when I pay off the laybuy. Hipod has one, the Ibiza, that would fit the bill, but I don't think Target had it on the shelves. Of course, the reason I went ahead and bought them today and didn't do my agonising multi-day search and online recce was that they were 20% off...