i replaced my Altis speaker yesterday. i must say go for speakers first.
i purchased poineer TS-D6902R cost me 10k
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TS-D6902R - 6" x 9" 2-Way Speaker | Pioneer Electronics USA
and i really felt the difference between these speaker and poineer 6975v2 and 6994s. if you want a enthusiast quality level go for them otherwise anyone you pick. please go to shop and ask if he can give you demo of these speakers. High-Quality Crossover Network really let you amaze the sound quality.
and for front i purchased pioneer 1674 cost me 3.5k
TS-A1674R - 6½" 3-Way Speaker | Pioneer Electronics USA
don't buy too much powerful speaker for front door otherwise door will make noise like plastic noise when vibrating. you need to have a good 2way or 3 way speaker at front.
i am using stock pioneer player in altis. the difference in quality is really superb. the perfect and clean installation is success to quality audio.
the screw should be tight and no vibration of plastic. make sure all clips are in place on rear panel and doors panel.
may be you can find these speakers cheap a bit. i didn't have time so i got from someone recommendation.