Maybe a Graco Nautilus? I was able to try DD1 in one the other day at Walmart and got it for her. She's almost 5.5 with a 16" torso (about 45" overall height, 44 lbs). She fits in the Parkway fine and usually rides in a Regent but had room to remain harnessed in the Nautilus, which is why I got it to use instead of the PW. I ran out of other HWH options for the vehicle the PW is currently in, so I'm happy to have found the GN to keep her harnessed a bit longer. I don't have exact measurements but the wings look to be set wider than the PW's. It would also make a decent booster once your DS outgrows the harness.
If you have LATCH the Monterey would be a great choice (from everything I've seen so far).
I don't have info on the Vivo, but there are lots of comparisons of various boosters over at car-seat.org - based on pics I've seen I'd guess that the Vivo won't offer much more room. The headwings are snug to offer good SIP.
ETA: The Graco Turbobooster fits a smaller kid well (not that your DS in particular is small, just that he (and my DD) are small/young compared to other booster riding kids) and the headwings aren't as snug as the PW's. It doesn't have the SIP that the PW has, though.
Another thought: Could your DS use earbuds instead of traditional headphones so they don't interfere with the wings? DD has never used anything with headphones, so I have no idea what the right thing for a kid to use is, but it was a thought.
Last edited by caleymama; 02-17-2008 at 02:32 PM.
mama to 2 lovely and loving DDs