I would probably spend the extra and get the SB17. Nicer (and round) cast frame, much better motor (Le is way lower), doesn't have a resonance issue just above 1kHz (blip in impedance and wiggle in frequency response).
Dayton RS180 has cleaner bass than an SB17, but the (upper) midrange isn't quite as good. I'd tend to use an RS180 in a 3-way and the SB17 in a 2-way (with subwoofer).
The next cheapest i'd go is the DA175-8. Similar bass cleanliness to an SB17, similar midrange to an RS180, half the price of both.