Re: Older low end PC, can I run all dlc on these specs (or at least add catsdogs)?
@Lightsims8 Stuff packs have a negligible impact on performance, and kits even less than that, so I'd say load up on both of these to your heart's content. Most game packs have a low impact, although the newer ones (Realm of Magic and onward) have a higher impact than the older ones. The oldest three expansions—Get to Work, Get Together, and City Living—are comparatively low-impact too, although they're more demanding than GPs.
Cats & Dogs is probably the single most demanding pack, and I really can't tell you whether it will run well or not. It's possible this one pack will push your game over the edge, or that it will be okay but you'll be close enough to the limit that adding more EPs isn't a good idea. There's enough variation in outcome from one player to the next that it's impossible to make predictions, other than when someone's machine is above the requirements for ultra settings.
In your position, if you really want C&D, I would buy that alone, install it right away, and see how it runs. Send a sim to Brindleton Bay and get a bunch of strays on the screen at the same time, then see what you think. Download a larger (but not massive) house from the Gallery and place a sim and pet inside, and play with them for a while. If the game is bogged down, you might be able to get a refund from EA customer support, although I wouldn't count on it. You could simply disable the pack and come back to it if and when you get a new computer.
Dream Home Decorator is somewhat broken, but not really in a performance-related way. If you're interested for the CAS or Build/Buy items, it's fine. If you want your sim to be an interior decorator, you'd probably run into some trouble on any machine. But it shouldn't seriously impact how the game runs overall.
Regardless of your decision regarding C&D, I would say add expansions newer than C&D one at a time, testing along the way to make sure performance isn't starting to drop below what you find acceptable. Buy all the SPs and kits you want, in one go, and test that content too. Buy a few GPs if you'd like, but not all of them, and test before adding anything else. You have some time; the spring sale ends March 28 at 10 am Pacific, according to the fine print on this site: