I've got two types of choices, that of expanding an army I already have or picking up a new one. I tend to plan my armies very carefully and for the most part I don't really have any urge to collect more then 2k of any given army. My opinion, typically, is that I would rather try something new and different then continue on something I already have.
Along that path I have had an urge to update my Chaos force (my oldest army, and the only army to survive all of my eBay purges) into a proper Khorne army. I also have been wanting for a while now to get some more Orks as they just don't work well at 1850. I need to dump my deff dread/killa kans and and add some bikes and another (or two) truck boyz to the list to make it work. I've also been considering getting some more IG, specifically some Russ' to play a slightly different IG force. I have a rather typical IG army and I think spamming armor 14 could be somewhat effective, simply because it's not seen that often. With the spread of missile spam it may be quite effective.
I've flirted a few times with Tau, and with the upcoming GW price increase Tau are being hit pretty hard so it may be a smart choice. I've also written about my desire to pick up an 1850 GK force. It would be pretty cheap (~$300) and easy to transport. 20 terminators and 3 dreadknights would be a fun force to play.
So in summary my choices are.
Expand an army.
- Orks - Add some bikes and truck boyz.
- IG - Leman Russ' five or six
- Chaos - Turn the army Khorne
- Tau - Battlesuit and Broadside army
- GK - Terminators and Dreadknights
Sometimes I wish I didn't like this hobby as much as a I do.