Congrats!
I am by no means an expert, but just having had my second child a week ago, I have recently done alot of carseat research!! This was my crazy version of nesting, I suppose!! :-)
There were two carseats that ranked very well with Consumer Report..the SnugRide (by Graco) and the KeyFit (by Chicco). When your daughter starts to shop, she will find that both of these brands make a bigger carseat that goes up to 30/32lbs (SnugRide 32 & KetFit 30). I DO NOT suggest those for you...they are bigger/heavier and since the triplets will probably be smaller than average, I doubt you will have the issue of them growing out of them before age 1. If you go with Graco, watch out for the seats that don't have a harness adjustment strap in the front (between the legs). I was surprised that many of the less expensive ones (all from Target!) sacrificed this feature and adjusting the straps from behind is a big pain ('times three' for you!!!)
Whatever you go with, remember they will not be able to use this infant carseat after they are 22lbs, although most people told me their kids grew out of them lengthwise first. In other words, you will need to get them a front-facing carseat sometime around 1 year (they now recommend rear facing as long as possible). Regardless, you may want to go cheap now & save your $$$ to invest in better convertable carseats since they will use these for a couple of years.
PS- The Graco "Safeseat" is the same thing as they Graco SnugRide 32...I called the company to ask and they are phasing out the safeseat name and replacing it with the snugride 32. I talked to a few moms who felt they had to go with the "Safeseat" because it was safer, but it really is not.
Goodluck!!