which turntable for the future?

@renatocomes, I have the same set up but did the Gert Petersen mod. As good as the MK IV is with the V arm, the mod addressed the bass and increased dynamics amongst other attributes. If you are DYIer, a short week of Sundays will bring the table, arm into your future. 

The Gyrodeck is a nice turntable but can certainly be improved upon.

As you value design/looks, the Oracle Delphi Mk VI is worthy of consideration.

The Clearaudio turntables also look and sound great.

A final suggestion is Vertere. I regret I haven't heard them but I'm very familiar with Roksan's and the Vertere's take the same design principles and improve on them.

Are regards the secondhand question, I would have no problem buying a secondhand deck from a reputable dealer. SME's in particular are built like tanks and will last for ever unless deliberately abused.

Of course your ears and eyes must judge what's right for you.

I like both my music hall mmf-7.3 and my Avid ingenium, all the turntable I'll ever need. If a turntable keeps proper speed, is well isolated, and has a decent tonearm, I cannot see spending any more than my two aforementioned tables. Both are well executed designs. I spend most my money on records nowadays. 

I spent a ton of time thinking about this last year. I emailed Mike Fremer and Michael Trei and got a lot of opinions. In the end, I was down to the Kuzma Stabi R with a 4pt arm or a Brinkmann Bardo. I ultimately found a demo model Bardo with the 10.5 arm and an ortofon Cadenza black that was set up by Mike Trei. The deal was too good to pass up. This table has changed my listening experience. The I didn't realize turntables could leoduce this kind of frequency response and the dynamics are stellar. If the price range you're looking at you could step up to a Taurus or even a Spyder in The Brinkmann line. I don't have the Kuzma but feel it would have been an equally good but different choice. As others have said, I'd avoid rhe VPI. They're super cool looking but ultimately don't perform to the level of some of the others mentioned on this thread. 

design is very important to me also.

the airforce is an ugly beast IMO.

first, I would go for an improved cartridge on your existing beautiful TT

any cartridge you buy can be used on any future table you buy.

your phono pre is extremely versatile, ready for any MC you might try. manufacturer will help you make the correct settings.

For my 1st MC Cartridge I chose AT33PTG/II.

Very wide separation, and very tight channel balance gives excellent imaging. I just bought another. I like it so much, I guessed my stylus should be worn, I sent it to AT, they agreed, just ready for discard. AT has a program, clean return for $40., or they sold me a new one for $262, less than half price.

I suspect you will fall in love with your existing TT again right away.