Hey man,

I've been playing my Yamaha TRBX174 for some time now, and im starting to feel something has to change. What would be an upgrade from that bass? Or would an upgrade be stupid at this point? Been playing bass around a year now, and im loving it.
It wouldn't necessarily be "stupid". If you are progressing to the point that you might start playing in a band then a back-up bass becomes important should anything happen to your main axe.

Sometimes upgrading your amp is a better idea than upgrading your guitar, especially if you are looking for more volume or better tone. Other times simply changing string types or brands can make a huge difference as well.

Your Yamaha is an excellent starter bass and would serve well in the role of backup bass. As to an appropriate upgrade, your budget will be a huge part of that decision. Are you ready for something like a MIA Fender Precision or Jazz in the $1,300 price range?

If not, then is $600 or less a better figure, or something in between? Knowing your budget will make targeting an appropriate upgrade bass easier.

Finally, a used MIM Precision or Jazz bass in the $300 price range is an excellent choice from the standpoint that it is a professional grade axe, better than your Yamaha and you will be able to recoup most, if not all, of your money back if you decide to sell it and haven't done a bunch of expensive mods to it. I recommend going this route if too many options is making it hard to choose.
Ah, I see you're in Denmark. What you are looking at is a Mexican Fender Precision and yes, they are nice basses. In the U.S. they can be found on the used market for about half of what a new one costs. Here in the U.S. they are $600 new. I recently bought one used for $275.

I don't know if the half-price-for-used formula holds true for your area or not but I recommend a little investigation on your part.

And... go find one in a music store and play it to see if you are going to like it.
That's a Mexican Jaguar. I have owned one. It is basically a Precision bass with a Jazz bass pickup added to the bridge. It has more versatility than a Precision bass because of the two pickups but you will have to decide for yourself whether or not you like the shape of the Jaguar body. Also, the Jaguar has a Jazz profile neck, which is more narrow than a precision neck (38mm versus 41mm). Both are about the same weight and the P-bass pickups sound the same in both basses.

So.. The Precision is a simpler system with a wider neck and millions of people love the Precision just the way it is.

The Jaguar has a narrower neck plus two pickups that will allow for more and different tones. It also has a more "modern" body.

I would say the width of the neck is the biggest reason to choose one over the other. Both are very good basses.