Phono pre amp

I've had both Rega and Schiit. Rega sounds better to my ears at comparable prices to Schiit. Rega Fono Mini is $195.00 brand new.Rega Fono MM is 445.00 brand new and Rega Fono MC is 555.00 brand new. I'm sure used prices will be around your budget.

I eventually upgraded to the Rega Aura.

Schiit Mani 2 -  $160. Michael Fremer of The Tracking Angle likes it!

An alternative to the Schiit models (which I happen like as well), you might want to look at the Parasound Zphono's, which you can pick up used for <$200.

Presumably your INT has a built in PS?

What is your amp and phono rig? 

I ask because for $650 + $150 shipping you could get a killer tube phono that will very likely beat anything built in.

Although the delivery timeline may be a non-starter. They only make a finite qty each month.

Softone Model 4 (made in Japan)

I’d try to persuade you to go at a higher level at this point....such as my K&K Trio.

At the time, it was considered to be 95% of Kevin Carter’s famous Max Phono, which was considered a bargain at $5k. The Trio sold new at half the cost of the Max. 

There are great deals to be had on used, high quality phono preamplifiers that will provide you years of enjoyment as/if you upgrade the other components in your system.