In other words look for a marker that you love straight out of the box without wanting a bunch of other crap on it
People like to say the same for every 'entry level' marker- buy cheap and buy upgrades.
No. Don't do it. You'll get a cheap marker, spend a fortune on upgrades that will probably do very little to actually bring the marker up to par, and then as stated above lose money.
Here's what I'd do if I were you-
First, as a few very wise people stated previously, get a good mask first. The Vforce Profilers and Grillz are both amazing masks that are still affordable. In fact, screw all the other masks out there, and get a set of Profilers- you will not regret it. Super comfortable, great field of view, takes about 5 seconds to disassemble for cleaning, and won't fog (unless it's super humid and you spend a lot of time standing still).
As far as markers go, the question to ask would be, do you want it right, or do you want it right now?
If you're really stuck on getting a cheap[er] entry/mid level marker immediately, than what I would do is get the best deal you can find, and then do nothing to it. Otherwise, there's no point as you'll eventually lose out on that 'good deal'.
The classic A5s, 98Cs, X7s, and others some have mentioned are definately robust, reliable, (the 98C is kind of like the AK of paintball ) and can be had for cheap, often in package deals with a pile of accessories.
On the con side, most of the semi-only markers are blatantly heavy. I know- I played multiple single games, as well as 2-day scenarios with an A5, and lugging it got old quick. Also I feel that offset hoppers really unbalance the marker, making it even more unwieldy. Also, while I don't think a new[er] player is going to get 'destroyed' using a semi-only marker, it definately is a disadvantage (for any level player) in todays increasingly electronic-dominated market.
You're also most likely going to run into some rather un-fun issues when you hit cold weather.
And finally, my pet peeve- run as fast and far from Kingman/Spyder as you can. I don't know if they've improved their "higher end" () stuff, but their entry level markers should only be used as paperweights.
If you're willing to wait, and save a little longer (seeing as how you have a steady job this shouldn't be a problem...), I would 200% recommend getting a high end electro. I guarantee you will see a marked improvement in handling (much lighter weight), reliability (especially in cold weather), and firepower (lets face it- he who shoots the most paint the fastest has the most fun ). All these things will make the game much more enjoyable and frustration free than other styles of marker, especially for a newer player. And the best part is, 90% of the time you won't have to worry about upgrades- most of the better electros are perfect as is.
And considering you can get a used (insert Dye/Planet Eclipse/Etc. here) for only $1-200 more than you're looking to pay, it would be well worth it to go this route, especially if you're looking to stick with this sport for the long run.
In fact, let me make a shameless plug for Planet Eclipse here- GO BUY ONE! NOW! You should easily be able to find a like-new 08 Ego, or Etek3 for around $3-400. However there is also nothing wrong with an 07/06 Ego or SLR either. Most people paid a lot for these markers when they came out and babied them, so many of them are still in excellent condition.
The Invert Mini, or Dangerous Power G3 series would also be good choices for a smaller budget.
Now granted, you're going to have a little extra expense for an electronic hopper and air tank, but both of these can also be had for good prices if you do a little looking.
Running HPA only for an electronic marker shouldn't be a problem at all, unless you play a lot of outlaw paintball.