SP10 MK3 recommendation

So I'm in the process of upgrading my analog set up. I just bought Albert's SP10 MK3 and I'm trying to decide on arm/cart combo. I'm freaking out a little because I don't want to make an expensive mistake.

My current arm from my last set up is a 10.5" Reed 2P. I might stay with this arm to start with, but I see a lot of 12" arms on the Technics tts so I'm not sure about the length. I'm also trying to decide on which cartridge. I'm leaning towards the Lyra Atlas or Airt Tight Supreme.

My current system is VAC Sig. IIa preamp and VAC Phi 300.1a amp. Speakers are Margules Grand Orpheus with Acuton (ceramic) drivers. SR ICs and Pranawire speaker cables.

So I'm looking for feedback about Reed arms with the SP10 tables and especially 10.5" arms.

Also looking for thoughts on synergy of Reed arms and the two cartridges mentioned above and in the context of the rest of my system.

Here's to a great (sounding) 2013 to all!
Graham Supreme in whatever length you want. You can also have multiple arm wands with carts already aligned and ready to go. It is also the only arm with a built in bubble level so you can get VTA spot on every record you play on the fly in seconds.
Thanks everyone for insights. They have been helpful....... to some degree! I know the bottom line and ideal circumstance is to have something on hand and see how it sounds in your system. This is especially important when getting closer to the end of system building,which is where I'm at. But sometimes this is not possible, and it is very helpful IMHO to get feedback from several respected sources
I have two MKllls and each is in a double arm plinth. I believe you have room for two arms as well on that Porter Plinth. I use some high end arms and cartridges. The PC-1 Supreme on the 312s is very good. I currently also enjoy the Benz LP-s on Reed 3P. Albert sells a really good imported unipivot you may ask him about. I have a Shelter 90x on that one and even the Ortofon M20 fl super is great on it at $175. No experience with the Atlas unfortunately.

One of the spots I reserved for the EPA 500 system which is somewhat dated and not as fully functional as the others but sounds surprisingly good. It's also affordable and very flexible. I rotate armwands in about 30 seconds. It's a great way to work in less expensive MM cartridges(Ortofon M20 fl super, Empire 4000 D/lll, Shure V15vxmr) or a mono cartridge(XV-1s mono). They all sound great.

Anyway, you should be able to set this up with performance and flexibility that will push the limits of most budgets. Have fun.
@rauliruegas so sony Pua-237 a very underrated tonearm? How good midrange bass and highs can you get with right cartridge?
The Thales Simplicity II sounds very very good on my SP10 mk3.

but you should do the Fidelis Analog MN6042 Upgrade.  High reliability modern upgrade/replacement for the Technics MN6042 Pitch Synthesizer IC.

  easily the best and cheapest upgrade for the wonderful SP10mk3.