those two are definitely a GREAT start if you want to be ambient. i would look into getting some sort of octave effect, the verbzilla does a great octave up reverb. also, the boss ps-3 does an awesome reverse octave up delay. all in all, i think that verbs and delays are the main pedals that you'll be looking into. oh, and make sure to pick up a volume pedal for swells!
Lots of stuff out there for all sorts of swirly ambient, dreampop/shoegaze and post-rock goodness.
Volume pedals, Modulation (Chorus, Flanger, Phaser, Vibrato, Pitch Shifter), Delay, Reverb, more Delay, more Reverb. Experiment with pedal order and settings. For example, placing a reverb pedal in the middle of your chain and one at the end will give you a floating Slowdive-like guitar sound.
Some pedals to consider:
Electro-Harmonix Stereo Memory Man w/Hazarai
Boss RE-20 Space Echo
Tech 21 Boost RVB
Boss PS-5 Super Shifter
MXR Carbon Copy
Electro-Harmonix The Clone Theory
BBE Mind Bender
Ibanez FL9 Flanger
Electro-Harmonix Small Stone
MXR Phase 90
Visual Sound Liquid Chorus
Electro-Harmonix Electric Mistress
Not pedals, but check out Simeon Harris in the U.K. He is an ambient/textural guitarist extraordinaire and his sounds via the Eventide Eclipse and TC G Force along with the Looperlative are stunning and simply gorgeous.
Okay here are some more pedal recommendations
Eventide Pitchfactor...if you have one you want to sell contact me.
Hardwire Delay and a hardwire reverb
Another delay such as a skrecho or dmm
A moog guitar is highly recommended for sustain functioning...check it out
possibly make the rig stereo
If you just get an M13 you'll not only save money but you'll be able to stack and change pedals all around to find sounds you've never even dreamed of. Stack 4 delays if you like. That will get you some great sounds for ambient music.
yeah, line 6 stuff isn't the hottest for that pro pro pro "feel", but is great for the heavy affected sounds. DL4 is awesome, M9 is awesome, M13 is probably awesome, but i've not played one. those and a VP and you'll be golden.
2nd the M13. Run with your rV-5 and an overdrive in the loop, and you will have endless ways to place reverb, delay, OD, another delay and another reverb (octo and particle are awesome for ambient) in that order... or other modualtions as well.
On top of an awesome looper, you have a HUGE assortment of FX.
Just did a gig with a local Dj who mixs on the fly and improv's sound/music by running a bunch of tracks together. He invinted me to play with him one night about 3 week ago. The owner of the tea shop were the gig was described it as aphex twins with robert fripp....my ego was stoked. So for 2 hours we just imporvised, damm was I beat afterwards one of the most draining gigs I ever did. Thing was I kept it simple and had a few things but got a lot of tones on the fly.To get a good rig I sat around the house and tested out gear to make a final rig . I used my old RE201 sapce echo, since unlike the ep3 or TTe it has reverb, so I was able to get repeats and a wash of ambinet reverb, alone or together. For modulation I picked my electric mistress it has a lot more unnatural sounds than my voddoo vibe CS9 or Phase 90. it did a swishes and woosh but got sounds that were more sythn than guita: rvery unpleasent and metalic which was perfect unlike the more organic phase vibe sound. I used a fuzz, tried a bunch ods n fuzz boxs Beano boost, almost unless for the joba whiich I suspected anyway,a Blue Dunlop fuzz face too shrill ,a rat ok, TS9 and Ts808 too blues rock, Used a GE twek o fuzz kit from small bear that I built. Had a wah and an EB volume ped. got tons of use from that that and the re201 realy were the most critical bits, fading in ideas and fading out as I played. I had a slide and an ebow too. The other key was my gutiar. I used a strat, since I had acess to the volume knob and a trem to shimmer chords notes and harmonics. I did bring my eletrci sitar too. 4 effects and an tape echo, pretty basic but it is easy to use live and gives a large range of tones. most key was avioding dorian mode soloing, think I played one proper solo the entrie night, think differently play less and play parts it's amazing what you can do with a basic set up.