Hafler preamp upgrades

I have this very rare preamp, is a Rockford Fosgate RF200 or also it was sold as Hafler JF200.
Is a op amp preamp
2 5532
4 TL072
6 LM833
IC LM393

The preamp got a good review, is there any room for improvements ?
I am open to suggestions

Are those red candy type of capacitors, film polypropylene ?
 

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  • Audio magazine rf2000 review.pdf
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