kaboodle is convience, purely in the fact you can goto a bunnings and get one. the quality is very dubious. I've never used it and probably never will
you can goto a cabinet maker and they'll spit you out a bunch of cabinets on the CNC with screw holes all wrapped up in shrink wrap with labels.
if you can do bathrooms etc you can do a kitchen, its just a bunch of carcasses with a benchtop, nothing too spectacular. I've watching someone do our's there's no way i'm paying someone to ever do one again.
Firstly: you also keep saying modern bench top, with out actually saying what material you want, you have just a laminet one now but are you planning on natural/man made stone?
secondly: most "stone" bench tops are mitred on the front to look thicker and hide where they sit on the carcass so you can just shim it to fit (or fill under the window with tile, benchtop material or no more gaps)
thirdly: replacing the carcasses is up to you, if you don't like their function, height or layout. there is no real standard height so you can factor in your carcass height and benchtop thickness to get your desired result. If you go for some off the shelf product like bunnings or ikea most are on adjustable feet so you can raise and lower them to help with leveling.