I haven't heard either but I just bought some Helix MTM kits (they'll actually be delivered today) and compared the two. From a numbers perspective, the Helixs have slightly higher sensitivity but the Apollos extend slightly lower. I went with the Helixs since I'll be running them with subs. I didn't see much (any?) reviews on the Apollo kits but the Helixs seem to be well regarded.
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