I tried a black sparkle Z3 5-string about a month ago when I got the itch for a Stingray but realized I didn't have $2,000 to spend on one. I have owned three Sires in the past, and still own one (a V7 Vintage 5 that I have turned into a Geddy Lee tribute of sorts). Overall, the build quality is excellent on Sires and they play and sound great. Definitely on par with basses that cost twice as much, maybe three times as much, depending on the brand. After watching hours and hours and hours . . . and hours of demo videos and comparisons between the Z3 and the Sterling Ray line of basses, I decided the try the Z3. It was hard to argue with the price. Build quality (of the actual bass itself) was great. The neck felt fantastic. However, living in Michigan, given that we're smack dab in the middle of the dry winter season, the neck within days began to shrink and make the frets uncomfortable. My V7 does the same. I know it's not uncommon, but I have not had that issue with any other bass. The biggest issue with the Z3, though, was the preamp. I thought it sounded great. I can't compare it to an actual Stingray, or even a Sterling, as I never owned both at the same time. There is a good demo video out there by Andertons that compares them. But the preamp crapped out on me with a couple of days and maybe an hour of playing. The volume knob got crackley and would cut out.
Sweetwater has excellent customer services, as most of us know, so I sent it back. I now have trust issues with Sires.
I replaced it with a used Sterling Ray35 poplar burl. It's a great sounding and feeling bass. I imagine it probably sounds a bit truer to an actual Stingray than the Sire, onacounta it's the same brand and similarly-inspired electronics. Whereas I feel like the Sire (according to the demos I've seen in comparison), sounds a bit more modern, polished, clean, for lack of better descriptors. Less gnarly of a tone than the Ray35. I tried a Sterling Ray35 a few months ago and did not like it (Blue Sparkle). It was heavy, and it felt like I was fighting it to get the notes to ring out. I don't have quite the same impression of the poplar burl variety, which is also lighter, around 9.5lbs. I'm totally speculating here, but I think it might be due to the finish. The sparkle blue was a thick, laquered finish, while the poplar burl is satin. Maybe the satin finish allows the wood to resonate better? I don't know. Maybe that's not a thing. But so far I'm really digging the Ray35, especially in series mode. The neck is solid and super comfortable all of the way up and down. I've used it at one band practice so far, and it sounds great. First gig with it is this weekend.
If you need something to scratch the Stingray itch on a budget, the Sire Z3 I'm sure is a good one, if you get one with a good preamp. They are insanely cheap. While the Ray35 might get you closer to an authentic Stingray tone. In the lower-tier or mid-level instruments, quality control is undoubtedly an issue. And weights can seriously fluctuate, which may or may not play a role in tone and enjoyability.
Short story long, if it were me, I'd get a Sterling Ray34 or 35 in a satin finish variety, and watch the weight (of either a Sire or a Sterling)