I think I can give you a fair assessment of that. I have a A3-300 and a Hsu VTF3.3, and have compared them directly. The LFM-1 EX is really just a downward-firing version of VTF3, everything else is almost exactly the same on the sub, the dimensions, the amp, the dual-ported design and tuning modes; it's a cloned design.
The A3-300 is a terrific sub, especially for how inexpensive it is, however the VTF3 is certainly a more capable sub, as well is should be, seeing how it's a bit more expensive. It's has a larger enclosure, two ports, variable tuning, and a more powerful amp. I have run bass test CDs, and the A3 will definitely chuff at 16 hertz and 18 hertz at volumes the VTF3 will have no problem with. Another thing I noticed is that the VTF3's cabinet is steadier, the A3's seem to vibrate a little bit above a certain amount of output. I suspect that the VTF3 could get louder with less problem overall, but I haven't pushed either sub to its maximum capability.
If the choice is between the A3 and the LFM-1 EX, you should go with the LFM-1 EX. Don't get me wrong, I really like the A3, but Outlaw's sale price on the LFM currently make it the very best deal in it's price class, in my opinion.