The Small Advent is a COMPLTELY differnent animal than a Baby Advent. The Small Advent had a NINE inch woofer, the Baby an 8". The Small Advent had the same tweeter as the Large Advent, the Baby a much smaller tweeter.
The Small Advent, IMHO, actually has better fidelity through the mids than the Large Advent. And it'll go lower than the 301, by far. It'll also have much more "accurate" midrange reproduction than the 301, and bass that is tighter (less boomy) than the 301 too.
Not that the 301 is all bad... far from it. There's ways to go FAR further wrong than Bose 301s... they're a decent, competant speaker. But the Small Advent is a REALLY GOOD speaker, not just merely competant...
Now, the Small Advent will need quite a bit more power than the 301... the 301 is fine, even on amps as small as 20-25 watts/channel, playing LOUD. OTOH, the Small Advent, I'd use at least 40-50 watts/channel. That's the only tradeoff, for more bass in basically the same size box...
Regards,
Gordon.