Today the last front speaker blew.
So i decided to replace them with some better speakers.
the speakers that came in the front doors were
Morel Dotech 6 ovation 140W

now, i have a 4 channel amp thats driving JBL 6X9 in the parcel shelf, and also driving the subwoofer (so no amp to the front)

How did the previous owner managed to run a 140W RMS speaker off the HU alone?

What are the Bridging options that i have on my HU?
Pioneer DEH 2000MP

I want to put in some infinity ref 6.5 up front, and although they are lower wattage then the MOREL, there is still some witchcraft to be done.

Does anyone have any idea how to do that (or how it was done?)

You can run speakers off the hu. However when you turn it up too much the hu can't handle it which is why it goes raspy and eventually the speakers blow. if you guna put decent speakers in the front then id suggest running it off another amp. however on my ba the 5x7s worked well with the hu but did chatter when too loud lol

what RMS should i go for?
5.7 are too rare here

I put 6x9's in my front doors

yes, however putting 6X9 in the front means high RMS draw with little in the way of available power.
My HU is 22W RMS X4 (possibly 44W RMS bridged)

does anybody have any experience with bridging HU outputs (front left and rear left for example) to achieve higher power?

Is JBL GTO8628 a good idea for front doors?

personally id amp the buggers!
i used to have an amp fixed to the underside of my pass seat never got in the way either and i could adjust everything with a screwdriver when i tuned it with a multimeter at 60hz..