A good trade?

Hi. I have the Polk LSi7 speakers and love the clarity and detail but miss the low end bass. A friend of mine has some Polk SDA 1b speakers with the cable and was wondering if I would get the same clarity and detail from those as I do from my speakers? We would be doing an even exchange.....speaker for speaker. I am powering my speakers now with a NAD 7045 receiver and was wondering, since they are both 4 ohm do you think I would be ok with the larger 4 ohm speakers? Thanks for all that help me out with this dilemma.