HiThomann t.racks DSP Mini 4x4 - 4 channel DSP for ca 70 Eur.
I do not think those boards have lower noise.
Part of the problem with active xo, is that sometimes you get strange artifacts on the frequency response.
Textbook filters do not always work that well, since the drivers you want normally to match are different in nature (Tweeter vs midrange vs woofer). They have different performance characteristics and will in 99% of the cases behave differently at a fixed frequency with a fixed filter.
A proper, well implemented old school filter using op amps and classic circuits for filter design may in some cases perform extremely well, but to finely hone the filters and adjust slopes and frequencies just so takes a lot of work and time.
For the sake of simplicity I strongly recommend using some form of DSP, in most cases you are guaranteed to outmatch conventional classic circuits, different filter slopes and values are way easier to just "try out", and in addition you gain the possibility to adjust and compensate for other flaws in the frequency response.
I do not think you will be able to get better noise figures using those boards you linked to, and they come with no box, no psu. The T. Racks 4x4 may be seem a bit more expensive, but the difference is probably negligible when you start adding work and other surrounding parts.
I have no first hand experience with the t.racks 4x4 mini. But it should be superior to the lower range minidsp products, another benefit is the balanced TRS jacks. Next real upgrade in sound quality would be DB Mark XCA, and similar in sq but better in build quality + increased functionality are the Driverack Venu360. Not much sense in getting anything more expensive than that, unless you want some very specific features.