Interconnects to use

Which interconnects to use matching Monitor Audio golds, Sherbourn amp, and Marantz av 8003? Also Rca or balanced?
I would contact the Cable Co and see what they recommend, based on the info in their database. Then I would utilize their service and try out their recommendations and see what you like best.
I would take a look at the offerings from Signal Cable company, well made and sane prices.
Both recommendations are great! I would go with MIT's AVT line of cables if you enjoy enhanced depth, imaging and natural tone. They will provide a wide warm and detailed soundstage...engaging and easy on the ears:O) Call Joe Abrams at Equus Audio, the best online authorized retailer with great discounts.
If the electronics support balanced connections, that would be my first choice and I'd use Belden 1800F

Speaker cable: Belden 5T00UP

Of course, you could choose to spend a lot more.

Monitor Gold 60s?

that tweeter is a bit hot in my opinion. Balanced is definitiely the way to go if possible... over RCA. The added bit is worth it. XLR too though like RCA, from cable to cable will offer some differences.

I had a KAV 250 Krell driving mine. at the time using Monster XLR. Clean clear, quiet, and exceptionally non musical.

Kept the amp... sold the speakers.... got Cardas Neutral ref XLR, and later, SR Resolution Ref x2 active XLR... and wish I hadn't sold the speakers. Then I sold the amp.

had I spent some time and effort looking into the area of a system I doubted was a significant portion thereof, I might have that combo yet.

I think you mated up better with the MA units... and you've not said waht range of $$$ is at hand, nor your sound preffs, or the intent here... music only, HT & music is my bet. IMO, then it could well be the SR res ref x2's. At their current pricing, they are a slam dunk no brainer choice in the under $550 $500 range. Read my reviews on ICs here on the 'gon they might help.

Cardas Neutral Ref is kind of my default cable... I think a pair of them should be in everyones closet or somewhere in their system if a solidly good budget cable is to be used with good to very good components. the name says it all. At less than $300 - 350 they're a good buy.

For less money, in XLR, check out the Audio Art offerings. I use the RCA version in my HT rig. Hard to beat for the $$$.

I'd suggest too... look into the power cord area of your system at some point. They can make as much or more impact. More usually. IMO
MIT cables are musical and now offer a 30day trial plus they are available for 40% off that's a deal:O)