If I went w/ the SkyBeacon, I'm giving up a new transponder for $1000 (the difference between the SkyBeacon and the 335/ESG options) and 1090. I live about 90 miles from Canada and, although I haven't flown there yet, I definitely see it happening in the near future. Other posts have said the necessity for 1090 in Canada isn't in place quite yet, but this may very well be time when penny-wise/pound-foolish kicks in. I'd hate to spend $1850, only to find out I need to spend another couple grand any way in a year or two.
Right now, my plane is IFR capable for VOR and ILS approaches, but I know GPS is slowly eating away at the maintaining of those facilities. I've completed about 1/3 to 1/2 of the IFR syllabus with my instructor in the plane, and am planning on continuing, if that helps shape any further advice.
Hmmm.
Right now, we don't know what Canada is going to require. Almost certainly 1090, but possibly antenna diversity as well. Right now, the diversity solutions are quite expensive - The only ones I know of are the NGT-9000D and the new Garmin GTX 345D. So, savings plus equipping for Canada right now is going to be difficult, and you will over-spend if you equip with antenna diversity and it turns out you don't need it for the flying you plan to do there.
I'm glad to hear you're working on your instrument rating - That really opens up a lot of possibilities to use GA for travel... But travel usually makes people want a faster airplane, too.
How long do you plan to keep your plane?
If you're at the limits of your airplane purchase budget already and you plan to keep it a long time, then I'd go back to suggesting the GNX 375. Not being able to fly a GPS approach at all is already very limiting, and in the next 10 years it will likely be severely limiting. For example, the last place I flew to was KSPW. It's a rare non-towered field with an ILS, but it has four runway ends. All four have GPS approaches, one has the ILS, and there's a VOR approach to the end opposite the ILS.
I landed, at night, opposite the ILS, with a pretty hefty wind. Because of the wind, the only two runway ends viable for landing would be the one I used, and one of the RNAV-only ones. Without any GPS capability, I would have had the option of a straight-in VOR approach with 800-1 minimums, or a circling ILS at night (see the "Lear down at TEB" thread for some discussion of why that's a bad idea) with 500-1/2 mins. With a non-WAAS GPS, the other runway became an option at 500-1, and the runway I landed on had 400-1 minimums. With a WAAS GPS, I could land on either one, with mins at 250-3/4 or 250-1.
And that's in the flatlands. The minimums can differ by a lot more at airports with more vertically developed terrain. Another recent example like that for me would be 1400-1 1/4 on the VOR approach, 1000-1 for LNAV (non-WAAS) minimums, and 200-3/4 for LPV (WAAS) minimums.
It's a HUGE difference in capability, even over a plane with WAAS GPS. Before I got my panel upgraded, I had a non-WAAS GPS and more than once I was the guy going missed when others with WAAS were getting in. And we haven't even talked about how much money being able to go GPS direct will save you over time. And if you end up deciding to sell your plane after all, it'll likely be a lot easier to sell, and fetch more money, if it's fully IFR equipped with a modern GPS and ADS-B In/Out.
Now, If you might be able to sell your plane and pick up a Comanche or something like that for better traveling capability, I'd probably go a different route, just finish your IR without a GPS and get the GDL-82 or Skybeacon. If your transponder happens to die before you sell the plane, you can get a nice GTX 327 pretty darn cheap these days. (I sold the one I pulled out during my upgrade for $250.) Since a nice, newer used transponder like the 327 is quite a bit cheaper than the difference between the GDL 82/Skybeacon and the GTX 335/Stratus ESG solutions, unless you expect to own the plane long enough that you're sure your existing transponder isn't going to make it that long, you're probably better off taking your chances and hoping it lasts until you sell the plane.
If you're keeping the plane "forever" and can't afford the GNX 375 right now, I guess the 335/Stratus ESG option, with a potential later addition of a GPS 175, might be the ticket... But it will cost more in total if you're doing two separate installations like that.