Yes, I have both the 4+ and the XP3 (the 4+ is in a 40-gallon tank). I don't particularly care for the 4+--it takes up precious room in the tank and doesn't do that great a job filtering (as you noted). (I don't care for any filters in the Fluval Plus series.) Internal filters can't compare to canisters, but a smaller tank limits what can be used sometimes. (But no filter is going to pick up all the poop from the bottom.)
I use the same MVB (T-Rex 100 Watt Active UV Heat bulb), but I could never get my turtle to bask under it if he were only 6 inches away--it's too hot for him. It would be good just to stick a thermometer on the basking area where he would bask under the light, leave it there for about 10-15 minutes and check the temp to see what it is...
Still waiting for some pics of your babies...