Mesa boards choice help

Hi, I'm running 2x lot port +bobs but add on lpt card died on me and I can't find  a replacement.

I'm tempted by Mesa Io cards and anticipating my pc dying too(it's core duo lga775 dell antique) I'm considering thernet cards 7i96s to be specific.
I like all on one solution with one cable for pc and not having to deal with chinesiumn BOBs.
Now, I was running 10khz servo thread, but I read that 1khz is "standard for Mesa ethernet 2khz possible and 4khz extreme, reported by one user here.
 I'm afraid that even at relatively slow feeds/rapids and accelerations I'll run into overshooting problems, in the end 1khz servo thread and 100mm/s rapid moves 0.1mm between updates. 
It's been a while since I went through the set up, so probably I'm mixing something important here but wouldt 6i25 be better at that respect?

If going 6i25 is there a DIY solution for getting analog out of this? I don't think I have it in me to rewrite after reinstal(I'm on lcnc 2.3) spindle vsd modbus module, and I suspect copy-paste may not works in later build..

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The 7I96S at 1 KHz should work fine unless you need extreme acceleration
(say > 5G)

Here is a plot of 1 KHz stepgen errors on a 7I96S at 20 IPS (= 508 mm/S)
with 240 IPS^2 accel (6096 mm/S^2) Note that the error (pink) scale is 10 uInch
per division ( 0.254 u per division)


 

@PCW thanks, i knew i was missing something and barking at the wrong tree.

@tommylight, thanks, Modbus was problem due to chinese VSD being fussy and needing 4 other coils set to change speed, with delays between each coil or it would just ignore it all, took me a week to get it working reliably.

I think i'll go with 7i96e/s just need to find one in resonable price and in stock. Used 5i25 would be cheapest but very not future proof.

Ordered!!