ur 850..
sc815...4x20 watts unless u have an r wagon
the following are pairs..
dash tweeter 1"
front door component midrange/bass 5-1/4" (altho many aftermarket 5-1/4" don't fit on not all but some cars)
rear door coaxial 5-1/4"
tailgate pillar tweeter 1"
the speakers are kinda odd shaped...
u should also have acs (active sound control), which helps keep sound level properly at different speeds

sc816...4x25 watts
now, i don't know about the actual speaker sizes of the v70, but the sc816 is similar to the sc815...
and the speaker sizes are much larger for the front door. it is a wide 7" so u can fit a very large speaker up front. i think the other positions are similar to the 850.


not much is that different. maybe the old speakers are just worn out...plus i'm sure the v70 is probably a little more quiet than the 850... i don't think the front speaker from the v70 would fit the 850, others maybe... also, the sc816 is probably in a different shade of grey than the sc815, so it wouldn't properly fit the interior color of the 850. if u wish to replace just the speaker, there are many good aftermarket speakers that are reasonable in price... switch out the doors and see if u find any difference... the front door is kinda shallow on some cars, so look for 5-1/4" with shallow magnets (like infinity's reference shallow 5-1/4" speakers) or 4" speakers to fit in the front door under the stock grill. the rear door speaker can be probably replaced with a 5-1/4" and still fit under the stock grill, there are adapters for the 5-1/4" (since it is more like a 6-1/2" opening) that should be able to help u fit it under the stock grill...just be sure to protect the back side of the magnet cause some water may come thru into the panel (which is why if u take a look at the rear door speaker there is a plastic shield over the top side of the speaker)..


good luck... that's just a simple plug n play... if u wish to have a more extensive upgrade, that's another story...