Thanks; that's a well-constructed post that can help not only yourself but others. Let me address your observation about the M50W first:
The M50W is the fastest-growing Swan model in the self-powered desktop category and a lot of this success owes to its high output and clear, clean sound. The woofer is substantial at the M50W's price and takes the design to another level. The satellites are quite good, and are similar to the more expensive H4 but in a different product package.
Con - Lack of reviews and feedback as it is very new
It's only TAI saying it, but the M50W is an excellent performer for under $300 and of course, we back them with a 30 day in-home trial guarantee.
Swan has not yet offered a smaller stand-alone multimedia woofer product we can use with other Swan models to create another 2.1 channel option, but that doesn't mean that another maker's small sub product wouldn't be a good idea for use with your favorite Swan 2.0 channel desktop satellites. Doing so opens up a lot of options, as you've considered.
Regardless of brand, and regardless of the fact that in many or most instances a "sub" isn't really needed with any 5.25"-based Swan desktop 2.0 system (everything from the D1080 series through the top T200b) a good bass system can take any of these products way beyond what we expect from affordable desktop sound.
So where does this leave us? IMHO, simply consider your budget possibilities and select the M50W if that's your limit. If you want better performance, if your budget can stand a larger expenditure, and especially if you plan on using a multi-channel front end and growing into 3.1, 5.1, or even 7.1, consider any 2.0 channel Swan model(s) joined to a separate small sub. It's literally a case of getting what you pay for because all Swan models in the 2.0 category scale very nicely in terms of sound versus cost. They just keep getting better as you ascend, and they do so, in our view, in a remarkably linear, predictable way.
The M50W is awfully hard to beat for the money, if it's even possible, and any decent sub that's cost has been added to any Swan 2.0 channel model tends to take over nicely in performance for proportionally higher cost. For example, a good quality sub is going to run at least $150. Added to the incoming new D1010-IV, you're at a little over $300. (From that baseline you can just go up and up). Depending on the sub's quality, that system should just outdistance the M50W. But if your budget is under $300, which many are, the M50W is, in our view, unbeatable.
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