Just my 2 cents
If you are IMC and want to see the current wx ahead, your only choices are radar, XM and ADS-B. The cheapest and most cost-effective is by far the latter.
It has certainly changed my own flying, but I also have StormScope which is useful for the fast-moving convective stuff.
If you're trying to plan you way around convective activity using anything other than real onboard radar, you're putting a lot of faith in potentially old information, for me I'm not going into IMC if I suspect there is convective activity.
XM, ADSB etc is for planning, it's not a real time tactical tool IMO
This is simply wrong and misguided. The ADS-B weather is a great addition to any SEL plane, particularly the NEXRAD. In the SE US it is an absolute game changer. If you go places, even occasionally, it is a valuable addition to your plane.
James331 is an experienced pilot and otherwise full of great insight but he reflexively compares NEXRAD to onboard radar which he has or has flown with in the past and considers it beneath his consideration. It's an opinion, but one I suggest you ignore.
This is true to a extent, I consider NEXRAD below onboard radar, I'm sure anyone who has flown both would agree.
Here is where I do like NEXRAD and similar, it's nice to pick up METARs and TAFs when you're out of radio range, still this is still more of a luxury than a necessity.
It's great for keeping a eye on weather over a hundred miles away and watching trends, I still think for a 150kt or slower plane you're not covering enough ground to need to look at weather that far ahead (almost more planning than close range tactical), even in that case, again a luxury over a requirement.
It's nice for keeping a eye on SIGMETS, again something ATC will provide if one pops up and your on freq.
So yeah, I like my ADSB, XM, etc, but it's really not 5k worth of like, for a grand or less and since I could write it off, I'd get it, but for 5k there are many things which will help with safety much more.
BAS belts
HID landing lights
HSI (if you're a IFR guy)
Put towards a nice autopilot with GPSS for single pilot work
Or best yet, spend some money on a CFI who has experience with long range GA IMC flying, you'll be a better weather pilot than just having a old radar image on one of the 50 screens in your plane.
With good planning and instruction you can interpret weather rather well with just your eyes, altimeter settings, OAT, GS vs TAS, etc.