If you're near Wilmington (U of Delaware?), that would be 2 hours away, or more in heavy traffic. If you have the time, and want to make the trip, just let me know when.
When I first started DIY, I had little experience. I stayed with tried & true speaker recipes designed by someone else. Building crossover boards was fairly easy to learn, but I found wood work was harder. Floor standing speaker cabinets, where all the parts fit tight and are square & vertical will be a challenge. (And then there's the finish.) Experienced wood workers know better how to recover from their mistakes

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Sub woofer(s) can always be added later once you know how the speakers themselves sound. The ER18 MTMs have an F3 (the bass frequency where they have dropped 3 dB in loudness) of 35 Hz, and they have useful bass as low as 31 Hz. With a powerful amp, that may be good enough.