With DD we brought a safe and sound convertible seat. With DS we hired out a capsual which came in handy (bout to give it back as we only got it for 3 months) but i wouldnt spend they money on buying one they arnt in it long enough.
We brought a maxi rider for DD to go into which will last her until she no longer needs to be in a seat. DS will then have the safe and sound car seat.