Ok first SSDs only help for start up and a few other things, games are not effected really. PSU (power supply) is important but try this DIY @ Newegg.com.
As far as adding a second card GPU (graphics card) as in Crossfire or SLI, every gamer and builder I have spoken to says it's not needed.
Heat sinks for your CPU and GPU are very important especially running FFXIV! My new GPU is running rather hot as the stock cooler is crap and my usual brand at the time I purchased my GTX 560 was not available. Case and room are important as well as is routing your wiring to keep air flow moving and cooling your components properly.
I have to agree with EVERYONE on here, build it yourself it's actually REALLY easy. Look at that link. See if your comfortable with what they explain and show. As other's have suggested, get anyone you trust that can and knows how to build you a great XIV PC with 1.4k. Any money you save, get a 2nd monitor, also really helpful when playing in game for ... omg SOOO much stuff this would become TL;DR. lol
Good luck!
Edit: Also as for SSDs, do some research on them. What I have read is Intel is best on market for not failing as much as others. There are also two different types of SSD. Here is a great article on SLC (single layer Cell) and MLC (Multi layer cell) SSDs and a quick wiki on SSDs. This will help a lot too in your decision.