What VPS would you recommend for me?

Hi,

My website is currently hosted on a VPS plan - I'm quite happy with it, as it's going well (though I really do need more RAM - 128MB isn't really enough for me), however, as it draws closer to the end of year (that I payed for), I've been looking around at other VPS deals which seem to offer better value (and have good reviews).
The issue is that I haven't been able to find a deal which suits me exactly, usually the ones being offered have too much of something and too little of something else.

To cut to the point, here's what I'm looking for:
- Preferably CentOS (cause I'm used to it, but I can get familiar with other distributions if need be)
- Min 20GB space
- Min 1000GB/month transfer (preferably 1500GB/month, but not sure if that's possible)
- Min 256MB RAM (512MB would be preferred)
- 1 IP address
- Willing to pay up to US$50/month
- Must accept PayPal
- Of course, must be reliable and fast

I can manage the server on my own, have little need for support and I don't need a control panel (in other words, I'd prefer not to pay the premium associated with any of these).

From looking at what's available, I don't think my expectations are too unreasonable, so I hope there's something which can suit me.