Yeah, a pop filter. Although not necessarily that one.
There's different qualities and sizes available.

Monitors you'll have to check around on. There's so many choices that you could go on forever. Edirol Ma-200 digital stereo micro monitors for instance if you wanna stick around the 2 - 300 mark. Dynaudio bm5a if you can manage a grand. Personally I prefer using a decent, audiophile amplifier and some audiophile speakers like polk audio or paradigm monitors. But there's also industry standards like Yamaha NS10's.

As far as whether to go with a standalone recorder, the only thing I can say is it's like the difference between going amateur compared to pro.
The computer recording is infinitely expandable. A standalone unit you're stuck with.
As far as computer recording goes, just the cut and paste option of editing is enough to sway me. There's nothing like being able to take a song and just remove the bridge and replace it. Or take the first verse and just copy and paste it 3 times to make up a whole song. Or doing a 16 part vocal harmony, using a vocal processor to put it in tune, adding reverb... cutting and pasting it so that it repeats in other parts of the song, copying it and dragging the copied part slightly behind the first so that you double everything up...
For instance, one song I did:

http://s93744050.onlinehome.us/SchmangeOnline/DarkBattleAlternate.mp3

then you can change the bridge just by muting some of the parts and adding new ones like harmonies

http://s93744050.onlinehome.us/SchmangeOnline/DarkBattle.mp3

.. was basically just one chord that I cut and pasted a dozen times, then ran it through a bunch of different VSTi synths. The only actual playing I did was to play an A chord on the keyboard and a few guitar chords. Everything else was drum loops, drawing notes into the editor and copy & pasting.
There's no way you could do that with a standalone.