I've seen in the past with the results on my table that a low SP can produce some amazing looking results with the formula we are using. One decent curation hit can send the reward/1000 SP owned into the late teens - as the above commentator can testify :)
The opposite is true with a very large account and I would suggest that any account with 20k+ SP cannot compete with a 1000-5000 SP account.
You are right about low SP having an advantage. With 15 SP you can score 1 full point per upvote. Or sometimes even 2 points.
However it would be good to give everyone the possibility to participate. So I would say create groups if necessary.
Where would you create the groups? If you could split 2/3 times? 100-500-1000+?
Not sure if I understand you correctly.
But groups like:
<100
100-1,000
Yes 3 groups of that hold active SP in those ranges.