The LCD-2C has about the same amount of bass as the Sundara, and a smaller soundstage, so I'd pass on that one.
You might have to go the used route to get the most bang for your buck. It's hard to get large soundstage and heavy bass on the cheap, as I've found that these features really seem to be incompatible. That being said, I think Hifiman's HE-500 or HE-560 might be just what you're looking for. The HE-500 is much harder to find these days, but it's among the best headphones I've heard, irrespective of price. Bass is absolutely bottomless, and has a good bit of power behind it (certainly more than the Sundara). The HE-560, while not quite as good, is much easier to find. Bass is very similar to the HE-500, though maybe a tiny bit less extension. You would really only notice this in side-to-side comparison though, and it's ttill a solid upgrade over the Sundara.
The biggest difference between the HE-500 and HE-560 is their treble response. The HE-560 has a bit of a spike in the 3khz region, while the HE-500 has very smooth treble. I didn't find the HE-560 to be overly bright, it just has a little bit more of a bite to it than the HE-500.
If you don't mind spending a little more on a used headphone, the Klipsch HP-3 ticks a lot of boxes, although not without compromise. Bass is extremely heavy for an open back and soundstage is very large, but treble is a little on the hot side and bass is fairly loose. The lower mids are accentuated, and the upper mids are down in level somewhat, so some people describe them as being recessed. They aren't recessed to me, they simply sound "full", but it is worth mentioning.