Josh
HSI = Horizontal Situation Indicator (If I remember correctly.)
Back when I ordered my instruments, there weren't any EFIS providers that offered engine gauges as part of their unit. Since then, just about everyone does. I could even convert one of my existing boxes to an engine module if I wanted to, but what would be the point, since I already have the other gauges.
Anyway, I think that just about all of the available EFIS packages are really great. I particularly like the Dynon D180 and the BMA Sport. However, as far as I know, and certainly it was the case when I ordered mine, BMA is the only EFIS manufacturer that offers an internal GPS w/ moving map as part of the overall unit, and at little or no additional cost, in their basic units.
If I was looking today, I'd have a hard time deciding what to go with. You can search the pages here and see a lot of opinions on quite a few different units, but a lot of it is personal taste and experience. Don't forget aesthetics! Looks do count for something, too!
For a simple Day/Night VFR, I think I'd go with a D180, Garmin 496, Garmin TXP and Garmin Comm. (Since I have the 496 already.) Otherwise, I'd go with a BMA sport and the radio/txp.
My advice, what ever you do, wait till the last minute to decide on the EFIS. You'll have to compare prices to see what fits your budget. Something new or updated comes up all the time and you want to get the latest stuff when you do buy your panel.
Sounds like you are thinking along the right lines.
Good luck.