Hi Micky . The Nikon cash back deal is really good. If it wasn't for Nancy wanting a bridge camera ( she finds the D90 too heavy) I would be thinking on getting another 7000.
Nikon speed lights are in a class of there own , I don't foresee an you won't have any problems with it.The SB 600 would be a perfect combination for a 7000, either wired or in commander mode, and you are getting it at a great price. Regards ... Graham
If you have Nikon film lenses go for a secondhand D7000 and it will drive the AF on them, if you don't then it all depends why you use a DSLR. Control? D7000, because it takes great pictures and you only ever use one lens but want to look through a conventional viewfinder, then the D3200 is Okay but the D7000 has 100% viewfinder, it is a pentaprism, bigger and brighter, has a diopter incase you need glasses, and at 16mpixels is excellent even in low light. You dont really want 24mpixels on an APS-C sensor as in low light you will think it soft and noisy. If money isn't an issue the D600 or D610 is streets ahead of the D7000 again. The D7100 isn't worth the extra £700 since the D7000 is now around £300 secondhand.