if you top up just 100 or so, you can actually change a whole component set

do you already have a component set and only have the tweeters spoiled?

what do you mean by "focus is on the back"? you mean the tweeter spoiled is on the back or front?

and no, component set for around 600-700 TOP UP rm100 from your existing rm500 budget

however if tweeters is your only focus, i believe you can get it for cheaper price. perhaps you can look up howie and see what kinda solutions he can offer.

most SQ setup would ignore the rear

like i said, if you're willing to top up a bit you can get an entire component set, or go on a budget and just replace the tweeters

tweeters alone probably less than 100-300 i believe

B&O?

Forget about upgrading your car la. With that sort of restriction on your car and budget limitation there's no way you can do better than the B&O.

Eh... wait, whats your budget again?

Cutting the door panel, need to revert what for change door? Even stock speakers will benefit from the mods mah. Anyway, the BMW direct replacement I saw was from AudioSystem, not BSW. It's not as expensive in comparison but no way comparable with that B&O.

I've seem plenty of stock looking BMWs both new and old with awesome sound systems in CV Audio. They specialise in high end cars anyway, my Wira was one of the rare cheapass cars they deal with. Kinda awkward parking my car to a R35 or a Alphard.  Conti cars like yours already have pretty good sound proofing so that's already half the battle won.

CV has excellent aftersales service. I'd deal with Peter from CV Audio anyday over the rude folks in KF. But that was me, perhaps they've improved since back then.

CV are pros with high end cars so I'd be comfortable sending an expensive Merc or BMW to them anyday.

I've also seen a 5-series stripped down in EA Autoworks too so I'm guessing they know what they're doing too.