The amount fields in Operations/VirtualOperations are still strings unfortunately (todo: have native types everywhere for v2).
So what you have to do is query all transactions for a time period, and then filter out the ones you need in your code.
Python Example:
from steem.amount import Amount
filter(Amount(x['amount']).currency == 'STEEM', lambda x: Amount(x['amount']).amount > 100, db_results)
I see, ok, Thanks man!