Wow, over 2K for a Sherline mill!!! It has extended range and is similar to the 2000 with regard to the head adjustments but I cannot imagine a Sherline mill costing that much.
I own a 5400 mill; got it maybe 25 years ago. It is a very capable mill, especially since I added the 15" column, column riser and headstock riser. It has done all I asked of it and maybe a bit more. In my opinion, what Sherline is doing with this 5800 mill is trying to expand the envelope of the machine without significantly improving the rigidity. Personally, I would opt for a PM25MV before I invested 2K in that machine:
http://www.precisionmatthews.com/shop/pm-25mv/. Or perhaps consider buying the 5400 and upgrading the column to give you more headroom if your work is going to be limited to the smaller stuff. Do not underestimate the 5400. It is a very capable little mill, but it is little and can only handle little stuff. Still, it will do everything that a bigger mill will do within its envelope and it will do it with precision.
On the off chance that you go with a Sherine mill, I think you would be better off without the package. Buy a better keyless chuck, like a 3/8" Rohm Supra and buy an adapter from Sherline for it. Also buy a good 2" screwless vise (an import will work fine); it will be more accurate and rigid than the aluminum Sherline vise. You will need a flycutter but buy the 7620 inserted carbide one; it is world's better. Save the clamping set for when you really need it; the vast majority of work can be held in the vise. I think a tooling plate is a wise investment and mine lives permanently on my table.
You can buy spotting drills instead of center drills and they will work better for starting holes. Sherline end mills tend to be good quality but are expensive for what they are. You can get better on ebay; ask the guys for recommendations. For tool holding, one of the best options you can get is a Beall ER32 chuck to fit the Sherline spindle. It comes with an import collet set but it is enough to get you cutting. I would not bother with Sherline's end mill holders; make your own if you want them but with an ER32 collet chuck you won't really need them at all. The books that come with the set are reprints of the instructions found on their website so I wouldn't let that influence me. However, you should by Joe Martin's book,
Tabletop Machining. It is an excellent primer that showcases Sherline equipment.
I love Sherline equipment. In the micro-machine line, I think they are the best out there (sorry Taig guys!). Their accessories tend to be high quality, work well and cost less than other small machine tool makers. I particularly like the 4400 long bed lathe and I think this is the best small precision lathe on the market in its size class. BUT this applies only if your work envelope is appropriate for these machines. If you need to or may need to go bigger, now is the time to go bigger.
I suggest you think on this, ask more questions here and then decide if these machines are appropriate for your needs. I own them, I love them, but I also own larger machines for when the need arises.
Welcome to HM, Adam!!