The SL-40 is comm only. The SL-30 is the SWEET comm/nav. It has a built-in CDI which will be fine for VFR, thus saving you another $1,500 for a remote CDI. You can upgrade later by adding a remote CDI to be IFR legal. Should you use a BMA or GRT EFIS versus the Dynon, you'll get an HSI capability now with bare minimum IFR ability with the single SL-30. You'll also be able to select radio frequencies through the EFIS. The SL-30 also has the ability to listen to 2 freqs at once. It's the next best thing to having 2 nav/comms. Everyone I've spoken with say there is no beating an SL-30 for value, power, performance and features.
Also, you might consider the VAL INST 421 combined with an ICOM A200. The VAL INST is an integrated CDI and NAV receiver while the ICOM is a flip/flop comm only. Both get great reviews from users and this combination will cost you about $3-400 less than an SL-30 but may provide fewer features. Of course, it will provide a full CDI, glide slope and marker beacon so maybe you get more value in the end.
Selecting your panel and comm nav stack can be the most fun and most frustrating part of the project. Just be careful though, it's also where most cost growth and budget overuns come from.
I started my build with the idea of having a night VFR panel with a 6-pack, a VAL INST 421 and a single ICOM A200 and I now have an IFR panel, GRT Horizon 1 EFIS, an SL-30, an SL-40, a KMD-150 (5 inch color MFD w/ GPS), GTX-327 and a PMA-8000B. The panel cost went from about $7 or 8K, all-up, to $24K. This can be an insideous phenomenum.
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