the stock no frills speakers are okay in your car if you get an aftermarket deck to drive them. I prefer Alpine but that is just me, its clean power without the silly "look at me I am an aftermarket stereo" lights that you find in the likes from JVC and Sony. Add a powered sub to the trunk driven off the deck pre-outs and you got a nice setup. Hi-pass the speakers at 100 Hz off the deck (alpine) and get one of those Infinity bass link setups and you will likely be much happier. Your problem will be if you send too much power to the stock no frills speakers, especially ones that have likely seen years of use and have tired surrounds.......the main reason I suggest the above. The premium audio packages from Volvo found in the 850s had Dynaudio speakers I believe.... which are damn good, its really too bad the newer Volvos dont offer Dynaudio (probably a Geely Holdings idea).

good deck from crutchfield with the Volvo wire kit and pocket for the dual din space - $199 with no tax or shipping - most have ipod interfaces as standard feature.

Basslink and 8 gauge power kit - maybe 250 or so....easy to install yourself.

I know you have a V70 but a few years back I dropped a modest but clean setup in a 98 S70. It sounded SOOOOOOOO Good I still miss it. The back decks of S70's have coaxial 8 inch drivers which do benefit from clean power and well.....yeah the car was well balanced and cranked.

Steve