I really like the JLC MUT Moon 39 in black. But if you have several other black dialed watches, then yes, I agree you should consider mixing it up. I really like the VC dress watches, especially the 1955 Historique. It is a true ultrathin, with a gorgeous, JLC-derived movement. Has real horological cachet too. Not sure what your budget is, but if this is in your range, I'd give it a serious look.
I'd say the dress watch is also 5-10k, trying to keep this however reasonable. On the other hand, that purchase would be probably for the next 20-30 years given the use, so I might splash a bit more. Have to find the VC price list, chrono24 talks about 20k+ on those Historiques so slighty over budget. Have to also say I looked hard at it, as the TWAT catalogue day also brought in the VC book. More into Patrimony, though.
As for sports watches, are you considering new or pre-owned or both? I'm not sure that one can get a new AP RO or VC Overseas in the 10K Euro range, but maybe there is much deeper discounting in your home country than in the US. I suppose if the 15300 is the one for you, then you will definitely be looking at pre-owned unless you find someone bought one and never wore it. The 15300 has been out of production for more than 3 years so the stock of new ones through ADs & Boutiques is long gone. Still if you can find a RO that you like in terms of design fit, and price then its a great watch. Its one of my favorite watches and is probably the most versatile one I own.
As for dress watches, I generally find white/silver more appealing. Sometimes dark dials can look a bit flat and boring on a dress watch, unless its something interesting like a stone dial, such as onyx or lapis, Also, white/silver dials lend themselves to showing guilloche much better than dark dials, and that can add some life to a white/silver dial. However, if you don't want a an all white/silver dial, you could always go with a VC Traditionelle with subdial at 6...which has a gray minute track to break things up a bit. Wishing you luck on your journey.
Sorry, forgot to mention: new (nothing beats peeling the stickers off your watch yourself...), price range is with discount. So you could drive a MSRP 15k€ Omega through that. AP 15400 is around 11-12k discounted, so it's a stretch. Chrono24 has one 15300 with stickers for sale in Europe, so I know this probably won't happen as new so I might have to review my policy on those. Or wait for next year's releases and see if the get back into more reasonable sizes.. 15450 was also interesting find in their range, haven't tried a 37mm RO so have to see if those are available here or I have to travel a bit.
For VC Overseas the non-chrono models are also below and around 10k, chronos are closer 15k, undiscounted. Haven't really tried to ask what the discount on those would be, but the non-chrono would fit the budget and I like their quality, but the design just is a bit wrong.
Very good point on the guilloche on white dials. Traditionelle / Patrimony are probably the VC bets for dress watch, and I think the simplicity would be the key here. Although I like ALS Saxonia Jahreskalender in platinum, but that would be for the "really over the top" category..
In general I'm trying to look really forward in my purchases and keep the collection to a few really quality pieces than go and buy something new every two years and then sell them away a bit later. That AP RO would probably be something which still stays fresh and timeless for a long time. Also, it looks good with white dial.
Edited by kimmo - 5/27/15 at 1:52pm