I'm getting a digital rebel 300D and I'm shopping around for a second
lens.  I've done some light 35mm SLR work in the past, and mostly have
been working on improving my framing and composition with a digital
Elph S230 over the past few years
(http://www.electrictao.net/gallery/portfolio).  I like landscape,
scenery, architecture, astro and people photos.  I don't generally do
any sports photos, though my fiance is an equestrian so I guess I'd
better start learning how to clean horse muck off my camera.  I also
like taking macro shots of flowers and insects, but I feel these tend
to be less challenging tests of composition.

I'm really excited about exploring photography more with the DR, but I
suspect  that the kit 18-55 isn't quite what I'm looking for.  Though
I like the idea of an 18mm wide-angle, I'm worried about distortion
and sharpness at the 18mm end.  Also, I'd like to have more of a
25-125 zoom for walking around.  I initially was looking for more of a
70-200/300 telephoto, but I figure I'm only going to use that much
telephoto for a small percentage of shots (i.e. wildlife shots), and
having a more compact, optically sound lens with smaller range was a
better option.

I know that I will get a Canon 50mm (1.8 or 1.4) and possibly a 20mm
wide-angle prime at some point down the road.  I'm also probably going
to get a mid-range telephoto zoom at some point (100-300mm), or I'll
just rent a 400mm prime from the local camera place for weekend
wildlife trips.  So the big question is, what to get as my second
(first non-kit) lens?  Here's what I've been looking at:

1. Canon EF 28-105 f/3.5-4.5; Pros: great reviews, great price, USM;
Cons: less zoom, no macro

2. Tamron SP 24-135 f/3.5-5.6; Pros: more range, sharp at 24mm, macro;
Cons: more $$, not so great above 90mm

3. Sigma 70-300 f/4-5.6; Pros: big lens with lots of range, less $$,
macro; Cons: would still have to swap lens for 35-50mm range shots, is
image contrast and sharpness sacrificed for the zoom range?

4. Tamron XR 28-300 f/3.5-6.3;  Pros: less $$, all-in-one lens, macro;
Cons: image quality at long focal lengths, and is such a wide range
really that useful/valuable? (I got an SLR for a reason, after all)

One thing I've noticed is that a lot of Canon's zoom lenses don't seem
to offer macro capability.  Is there a reason for this?  Any tips on
getting around this limitation (e.g. dedicated macro lens, etc.)?
Also, any advice on how well/how poorly macro multifilter sets work
would be appreciated.

I have a Meade ETX-90 telescope for casual observing, and it doubles
as a 1250mm f/13.8 spotting scope, but I have no idea how well this
works on terrestrial targets and with a dSLR.