Well yes and no, you have 6" now, they call them 6x8 but they are 6" as far as bass goes.
You can go with round 8" for more bass, not subwoofer bass, just more bass that with 6".
These are all 2-way speakers.
Or you can add a powered sub, which would give you more bass than even 8", it has to do with the design.
So you would add powered sub to either 6" or 8" 2-ways for more bass.
It is like home theater, surround sound is nice, but add a powered sub and just using the TV speakers with sub most people would think Home theater setup, lol.
Because that is what is lacking with smaller speakers, a presents, lower frequencies are what our ears tell us is "power" and richness, i.e. thunder.
Crack of lightning is one thing the rumble of thunder is where the "power" is, lol.
Article here 0n ranger speaker swap: http://www.therangerstation.com/Maga...t_speakers.htm
Most powered subs can be hooked up to closest speakers wires, just splice two wires in, and that goes to subs 8ohm connection.
It doesn't effect the stereos amp because it is not actually an 8ohm connection, it is a transformer.
And of course a fused power wire.