I am the same, was looking at the Rainbow, the Audison and the Helix Match series for front components.
From previous experience, just adding tweeters make a big difference, although on this car I would like to pre-plan potential future improvements (ie amp)
I like the idea of an amp that just plugs into existing OEM harnesses and works without fuss, or minimal wiring through the car hassle.
Given the fact it's a stereo so is amp'ed from the HU only, cheap options do not seem plentiful!
I don't mind spending a couple of hundred quid, but the amps recommended are usually 500/£600+ and when you then factor in speakers, it becomes too expensive to justify.
Might just start with the fronts again and see how bothered I am later down the line.
FWIW the door trims with tweeter housing can also be had without the HK branding, I personally prefer it without if they are not HK speakers, as no point it saying HK when the speakers are Rainbow
