What other benefits does user get?
More and better visibility probably. Though I have seen people with upwards of 1000SP here and even they have to use bots to upvote their posts.
The only upside I can think of is that Steem going upwards of $50 and then only you can see direct benefits of your Steem Power (which can be availed only after a period of 98 days)
That it is. How about power to choose how much payout you want to give to your upvotes?
Use Busy.org instead of Steemit.com. You can choose your upvote value even if your SP is below 500. Alternatively, you can simply start using steemauto and add any number of users you want to at your desired upvote %.
I will recommend you use the both methods.