Ok. Went to Segedins on Dominion Rd - they're Supercharge retailer. They have MF52 (CCA600, RC105) for $142+GST. Asked a sp to test my battery - green colour, the battery is alive :-\ though it's from 2007 (found a sticker on it).
Bosch S3 is $127 installed but it's only CCA300.
Half an hour prior to going to the shop played with this thing for a few minutes, a few open-close rounds - the car just started, one more "open-close" and it probably wouldn't start at all. A few weeks ago I was replacing a pollen/cabin filter - cabin lights on for maybe half an hour 45 min max, music off, aircon on for max 10 min - had to jump start the car after that, just wouldn't start at all. If the battery is still OK what else could it be? I assume replacing my current battery simply won't cure the issue (or it would?)
After browsing the forum my understanding is that something sucking juices from the battery (an alarm, a stereo or lots of other possible things) and that it's pretty hard to eliminate that bloody "sucking juices something". :-\ Especially without any appropriate knowledge.